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Biomedical subjects

A Boag

Publications and source records attributed to A Boag.

8 recordsLinked to original sources
PubMed2006

Brain and spinal cord haemorrhages associated with Angiostrongylus vasorum infection in four dogs.

Multifocal haemorrhages associated with Angiostrongylus vasorum infection were observed in the central nervous system of four dogs with neurological signs including depression, seizures, spinal pain and paresis. In magnetic resonance images the majority of the lesions were isointense or slightly hyperintense in T1-weighted images, hyperintense in T2-weighted images and hypointense in T2*-weighted (gradient echo) images, compatible with haemorrhages more than seven days old. Lesions were found in the brain of three of the dogs and in the spinal cord of two. The cerebrospinal fluid contained high concentrations of protein and evidence of erythrophagia. All the dogs had coagulopathy and pulmonary haemorrhage of varying severity. A vasorum larvae were detected in the faeces of each of the dogs. Neural A vasorum was confirmed at postmortem examination in two dogs.

Angiostrongylus↗
PubMed2003

6-mercaptopurine and inflammatory bowel disease: hidden ground for the cytomegalovirus.

6-mercaptopurine (6-MP) and azathioprine are important drugs for the treatment of inflammatory bowel disease (IBD) but their actions suppress host defense against infection. A challenging case of a 19-year-old female patient with quiescent Crohn's disease maintained with 6-MP presenting with dyspnea and a normal chest exam and x-ray is presented. She became ventilator-dependent and only after numerous investigations was diagnosed with cytomegalovirus (CMV) pneumonitis. A systematic literature review of CMV infections in IBD patients was performed. The present case is the first report of a patient with quiescent IBD maintained on 6-MP who developed CMV pneumonitis. Other reports have identified patients with active disease on multiple immunosuppressants who developed CMV pneumonitis and also highlight the risk of CMV colitis in refractory IBD. The authors review the approach to the diagnosis of CMV infections in IBD patients with atypical pneumonia and colitis and highlight the importance of considering CMV infection in these settings.

Adult↗
PubMed2001

Narrow-band microcavity waveguides in photonic crystals.

A novel device, formed by a widely spaced periodic array of defects in a photonic bandgap crystal, is studied with the goal of designing a waveguide with a prescribed narrow bandwidth. Tunneling of radiation between the defect sites allows wave propagation along the line of the defects. An analytical study based on the weakly coupled cavity model is performed, and the dispersion relation omega(beta) of the new waveguide is derived. The frequency shift and the band structure of the periodic defect waveguide are linked by an analytic relationship to the distance between the defect sites and therefore can be tuned by varying the latter. Sections of such waveguides can be employed as ultra-narrow-band filters in optical routing devices. Numerical simulations demonstrate the performances of this new device and support the analytical predictions.

Journal Article↗
PubMed1996

Coexpression of hepatocyte growth factor and receptor (Met) in human breast carcinoma.

Expression of hepatocyte growth factor (HGF) and HGF receptor (HGFR, product of the met proto-oncogene) mRNA were examined by nonisotopic in situ hybridization in a spectrum of benign and malignant human breast tissues. mRNA for both HGFR and HGF was detected in benign ductal epithelium. Epithelial expression of HGF mRNA was particularly intense in regions of ductal epithelial hyperplasia. Positive expression of HGF (but not HGFR) mRNA was also found in adipocytes, endothelial cells, and to varying degrees in stromal fibroblasts. In 12 of 12 cases of ductal carcinoma in situ and infiltrating ductal carcinoma, carcinoma cells showed a heterogeneous pattern of expression for both HGFR and HGF mRNA. In infiltrating ductal carcinomas, intense expression of HGFR mRNA was not restricted to ductular structures but as also seen in non-duct-forming carcinoma cells. The same zones of the tumors (most commonly at the advancing margins) that expressed strongly HGFR mRNA often were also strongly positive for HGF mRNA, suggesting a possible autocrine effect. The expression pattern of HGFR protein in 25 cases including the same series of tissues used for in situ hybridization analysis was similar to that of HGFR mRNA, as determined by an immunoperoxidase technique. The finding that HGFR is expressed by both benign and malignant epithelium, and its not restricted to duct-forming structures, suggests that, although the potential for HGF/HGFR binding is maintained in malignancy, the response to ligand binding at the level of the receptor or the cellular response to receptor activation may change at some point during progression.

Breast↗
PubMed1993

Analysis and optimization of waveguide multiapplicator hyperthermia systems.

A method is proposed for determining the excitation coefficients of an antenna array operating in a large rectangular waveguide and used as a hyperthermia system. The excitation coefficients of the array elements are optimized for attaining an improved specific absorption rate (SAR) distribution around a deep-seated tumor. The method is applied to a two-dimensional problem of a piecewise homogeneous post in a waveguide representing a section of the human torso. The array is operating below the cutoff frequency of the dominant mode of the waveguide. Numerical simulations have been performed to check the effectiveness of this approach. The results show that by using the proposed optimization method, SAR distributions can be improved.

Electromagnetic Fields↗
PubMed1990

Optimal excitation of multiapplicator systems for deep regional hyperthermia.

A method is proposed for determining the excitation amplitudes and phases of the elements of electromagnetic multiapplicator systems for optimizing the specific absorption rate (SAR) distribution around a deep-seated tumor. In this method, the ratio of the power dissipated in the tumor to a weighted summation of the powers supplied to the surrounding regions is optimized. The optimization procedure is combined with a recently proposed effective technique for analysis of various electromagnetic scattering and interaction problems. The general principle is applied to a two-dimensional problem of a piecewise homogeneous cylinder heated by an array of electric current filaments placed outside the cylinder. Numerical simulations are performed to check the effectiveness of the approach. The results demonstrate that using this optimization method, improved SAR distributions can be achieved. The extension to three-dimensional configurations is discussed.

Electromagnetic Phenomena↗