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Biomedical subjects

Peter J McDonald

Publications and source records attributed to Peter J McDonald.

6 recordsLinked to original sources
PubMed2006

Observations of coarsening of air voids in a polymer-highly-soluble crystalline matrix during dissolution.

A combination of magnetic resonance imaging and x-ray microcomputed tomography has been used to visualize the development of the internal micro-structure within compressed tablets made from a combination of insoluble particles (Eudragit, a polymer) and soluble particles (diltiazem hydrochloride, a drug), during dissolution in water. Air voids in the tablet are seen to coarsen. The size distribution of the air voids is well fitted by a log-normal distribution with a mean size that grows linearly with time. There is evidence for both diffusion of voids and sudden collapse of individual voids, presumably as they coalesce. The behavior of the voids is studied and compared with models of coarsening; the implications for tablet dissolution are considered.

Journal Article↗
PubMed2004

Up-regulation of collagen and tissue inhibitors of matrix metalloproteinase in colonic diverticular disease.

PURPOSE: Thickening of the muscularis propria is a key pathologic feature of colonic diverticulosis but its cause is unknown. This study was designed to investigate the role of collagens, matrix metalloproteinases, and tissue inhibitor of metalloproteinases in colonic diverticulosis. METHODS: Collagen content was determined by Sircol Collagen Assay and standard van Gieson staining. Messenger-RNA expression for matrix metalloproteinases and tissue inhibitor of metalloproteinase was analyzed by quantitative competitive reverse transcription polymerase chain reaction. Immunohistochemical staining was performed to localize tissue inhibitor of metalloproteinases in sections. RESULTS: In mucosa and submucosal layer, complicated diverticular disease samples had a higher collagen content than uncomplicated disease, which in turn had higher levels than controls. There was an 18-fold increase in tissue inhibitor of metalloproteinase-1 mRNA, and a threefold increase in tissue inhibitor of metalloproteinase-2 mRNA in complicated diverticulosis compared with controls. In the muscularis propria, the amount of total soluble collagen also was higher in both uncomplicated and complicated diverticulosis samples than in the controls. Tissue inhibitor of metalloproteinase-1 and metalloproteinase-2 mRNA was significantly increased in diverticulosis compared with controls. Macrophage-like and fibroblast-like cells stained strongly positive for tissue inhibitor of metalloproteinases in the submucosa, serosa, and muscularis propria and in areas around the blood vessels. CONCLUSIONS: Colonic diverticulosis is associated with altered collagen content and tissue inhibitor of metalloproteinases expression. These factors may play a role in remodeling the gut wall in this condition.

Aged↗
PubMed2003

Measurement of the diffusion of liquids into dental restorative resins by stray-field nuclear magnetic resonance imaging (STRAFI).

OBJECTIVES: The purpose of this investigation was to determine the diffusion mechanism for water/ethanol mixtures in a diacrylate dental resin by direct observation of the absorbed liquid profiles using NMR microimaging. METHODS: Frequency-swept stray-field magnetic resonance imaging (STRAFI) was used. Solutions containing 25-65% by volume ethanol remained in contact with visible light cured 54% TEGDMA: 46% modified TUDMA sheets while measurements were made. The diffusion profiles were recorded periodically for diffusion times up to 10 h, to a depth of 360 microm and with readings taken at 24 microm intervals. RESULTS: For all liquid mixtures, diffusion was found to be Fickian with coefficients that increased progressively and smoothly with alcohol content in the diffusing mixture, from 2.4 x 10(-13) to 150 x 10(-13) m2 s(-1). A rule of mixtures approach, as suggested by Kwei and Zupko, gave a satisfactory description of the ethanol fraction dependence of the diffusivity. SIGNIFICANCE: Frequency-swept STRAFI offers a new and unique opportunity to produce spatially resolved measurements of the liquids in dental resins to high resolution. In this study, absorption was investigated since an understanding of its mechanism is fundamental to limiting consequent environmental degradation. STRAFI has great potential for other applications, for example drying, liquid exchange, etc. Since STRAFI can discriminate 1H in the liquid from those in softened polymer additional applications are envisaged.

Acrylic Resins↗
PubMed2003

Patient perceptions of MRSA.

Drug-resistant nosocomial infections are an increasing problem. This issue has received considerable media coverage. To our knowledge there have been no studies investigating patient awareness and perceptions of nosocomial infections. A total of 113 surgical out-patients completed a questionnaire stating whether they had heard of either superbugs or MRSA. A series of questions were asked about the source of any information; methods of transmission and prevention; the consequences of infection and their emotional response if they were to acquire MRSA. Fifty patients (44%) had heard of superbugs or MRSA mainly via the media (58%) or from hospital staff (44%). The majority would feel either angry or afraid if they acquired MRSA in hospital, but there was good awareness of both methods of infection control and the consequences of infection. From our study, we conclude that the media is at least as important as health professionals in providing information. Concerns regarding nosocomial infection may need to be addressed prior to admission.

Adult↗
PubMed2002

The effectiveness of coordinated care for people with chronic respiratory disease.

OBJECTIVES: To evaluate the effectiveness of coordinated care for chronic respiratory disease. DESIGN AND SETTING: Community-based geographical control study, in western (intervention) and northern (comparison) metropolitan Adelaide (SA). PARTICIPANTS: 377 adults (223 intervention; 154 comparison) with chronic obstructive pulmonary disease, asthma or other chronic respiratory condition, July 1997 to December 1999. INTERVENTION: Coordinated care (includes care coordinator, care guidelines, service coordinator and care mentor). MAIN OUTCOME MEASURES: Hospital admissions (any, unplanned and respiratory), functionality (activities of daily living) and quality of life (SF-36 and Dartmouth COOP). RESULTS: At entry to the study, intervention and comparison subjects were dissimilar. The intervention group was 10 years older (P < 0.001), less likely to smoke (P = 0.014), had higher rates of hospitalisation in the previous 12 months (P < 0.001) and had worse self-reported quality of life (SF-36 physical component summary score [P < 0.001] and four of nine COOP domains [P = 0.002-0.013]). After adjustment for relevant baseline characteristics, coordinated care was not associated with any difference in hospitalisation, but was associated with some improvements in quality of life (SF-36 mental component summary score [P = 0.023] and three of nine COOP domains [P = 0.008-0.031]) compared with the comparison group. CONCLUSIONS: Coordinated care given to patients with chronic respiratory disease did not affect hospitalisation, but it was associated with an improvement in some quality-of-life measures.

Activities of Daily Living↗