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Biomedical subjects

M B McDonnell

Publications and source records attributed to M B McDonnell.

4 recordsLinked to original sources
PubMed2005

Development of a novel compact sonicator for cell disruption.

Ultrasound microbial cell disrupters operating at around 20 kHz are often physically large and, due to significant heating, can be unsuitable for small sample volumes where biochemical integrity of the extracted product is required. Development of a compact device based on a 63.5-mm diameter, 6.5-mm thick tubular transducer for rapid cell disruption in small-volume samples in a high-intensity acoustic cavitation field with minimal temperature rises is described here. Suspensions of Saccharomyces cerevisiae were exposed to cavitation for various times in the compact device and a 20-kHz probe sonicator. Cell disruption was assessed by protein release and by staining. Yeast cell disruption was greater in the novel 267-kHz sonicator than in the 20-kHz probe sonicator for the same exposure time. A 1-dimensional (1-D) transfer matrix model analysis for piezoelectric resonators was applied to an axial cross-section of the tubular sonicator to predict frequencies of mechanical resonance in the sample volume associated with maximum acoustic pressure. Admittance measurements identified frequencies of electrical resonance. Ultrasonic cavitation noise peaks were detected by a hydrophone at both the mechanical and electrical resonances. Cell breakage efficiency was twice as great in terms of protein released per dissipated watt at the mechanical resonance predicted by the model, compared to those at the electrical resonance frequencies. The results form a basis for rational design of an ultrasound cell disruption technique for small-volume samples.

Erythrocytes↗
PubMed1991

pH dependence of hydrochloric acid diffusion through gastric mucus: correlation with diffusion through a water layer using a membrane-mounted glass pH electrode.

Solute diffusion coefficients (D) can indicate a dependence upon actual solute concentrations. Here a single compartment has been utilized, in which effective HCl diffusion to a membrane-mounted glass pH electrode can be measured across the pH spectrum. The study has investigated HCl diffusion through both mucus and water layers as a function of HCl concentration. The observed dynamic responses of a liquid-film and mucus-coated electrodes over a range of HCl concentrations suggest that the speed at which equilibrium is attained is pH dependent; equilibrium was reached rapidly under more acidic and alkaline conditions. Estimated values of DHCl also indicate a strong pH dependence for both liquid film and mucus. In both instances, a greater than 10-fold reduction in DHCl at pH 7.5 as compared with that at pH 3.5 has been demonstrated. Furthermore, estimated values of DHCl are approximately 4-fold smaller through the mucus gel, as compared with a water layer. The findings indicate that the most powerful influence on diffusional resistance is pH itself, whereby a marked drop in H+ diffusion is likely to occur towards neutral pH irrespective of the composition of the gel barrier. Possible implications of the findings are discussed in relation to mucosal protection from acid.

Animals↗
PubMedDate not supplied

The association between depressive symptoms and health status in patients with chronic pulmonary disease.

This study evaluated the association between depressive symptoms and health related quality of life (HRQoL) in patients with chronic pulmonary disease using both general and disease-specific HRQoL measures. A cross-sectional analysis of HRQoL measures completed by patients enrolled in the Department of Veteran Affairs Ambulatory Care Quality Improvement Project. 1252 patients with chronic pulmonary disease screened positive for emotional distress and returned the Hopkins Symptom Checklist-20 (SCL-20). 733 of 1252 had a score of 1.75 or greater on the SCL-20 indicating significant depressive symptoms. Depressive symptoms were associated with statistically significantly worse general and pulmonary health as reflected by lower scores on all sub-scales of both the Medical Outcomes Short Form-36 and the Seattle Obstructive Lung Disease Questionnaire. In fact, 11% to 18% of the variance in physical function sub-scales was attributed to depressive symptoms alone. Patients with chronic pulmonary disease and depressive symptoms reported significantly more impaired functioning and worse health status when compared to those patients without depressive symptoms. Because there are highly effective treatments for depression, selective screening of patients with chronic pulmonary disease for depression may identify a group that could potentially benefit from treatment interventions.

Adaptation, Psychological↗