Computational Modeling and Validation of Thermally Induced Electrical Capacitance Changes for Lipid Bilayer Membranes Irradiated by Pulsed Lasers.

Neural stimulation has widespread applications in investigating brain functions, restoring impaired neural functions, and treating numerous neurological/psychiatric diseases. Use of infrared pulses to stimulate neurons (infrared neural stimulation) offers a direct and non-invasive technique. Recent research has demonstrated that transient heating associated with the absorption of infrared light by the local aqueous medium around the cell membrane can stimulate nerves. One mechanism for this stimulation is due to a thermally induced increase in the membrane electrical capacitance, which causes cell depolarization as well as action potential production under certain physiological conditions. A theoretical and computational model helps better understand the mechanism of thermally induced electrical capacitance changes and optimize the stimulus parameters. In this article, we develop the existing theoretical models for membrane electrical capacitance and its thermally induced changes. We improve the formulation of Gouy-Chapman-Stern theory by Genet et al. and Shapiro et al. with the addition of a diffuse layer to the electrical double layer and by modifying the relation of Stern layer capacitance, to calculate the membrane capacitive charge and capacitive current. We also present a new method to calculate the membrane electrical capacitance and the rate of its thermally induced changes. In our calculations, two new factors are considered including the temperature dependence of the surface charge density and the hydrophobic core dielectric constant of the lipid bilayer. Our developed model predicts rates of 0.3 and 0.26%/°C for the thermally induced capacitance changes of the artificial lipid bilayer under two different sets of conditions previously reported by Shapiro et al. and Carvalho-de-Souza et al., respectively. Our model is in very good agreement with the corresponding experimental values given by these groups. The presented model is also able to calculate the membrane capacitive currents and investigate the voltage dependence of this current.

Pulmonary Nodules as an Initial Manifestation of Behçet's Disease.

Behçet's disease (BD) is a systemic vasculopathy, characterized by recurrent oral aphthae, genital ulcers, uveitis, and skin lesions. Although vascular involvement, including venous and arteries of any size, is a usual manifestation, cases with pulmonary thrombosis as the initial symptom are not common in the absence of pulmonary artery aneurysm (PAA). This report describes a 36-year-old man with recurrent fever, nonmassive hemoptysis, and persistent cough with lung nodules in CT scan who had undergone open lung biopsy. On the basis of morphological findings, BD was suggested and more precise evaluation confirmed the diagnosis.

Lung donation and causes behind its failure: a single-center experience.

INTRODUCTION: Brain-dead patients are almost the only source of organs for lung transplantation, and lungs fall within the area of the least harvested organs. As a result, maintaining the highest possible harvest rate is a must for the lung transplantation system. In the present study, the harvest rate of lungs and also the causes of failure to donate the lungs is reported for brain-dead patients in our organ procurement unit. MATERIALS AND METHODS: After going through the brain-death database at our organ procurement unit between 2004 and 2008, we included all 93 brain deaths in this hospital. The lung donation rate was reviewed to examined the causes for failure to donate lungs. RESULTS: From the total brain-dead patients registered in the database, only 4 (4.6%) patients donated their lungs. The causes of failure to donate a lung were not suitable lungs among 78 (83.8%) because they had an unacceptable oxygen challenge test results (<300 mm Hg). Another 11 patients had acceptable oxygen challenge test results, but donation failed in their case as well due to most frequently to pulmonary aspiration. CONCLUSION: In this center, only a small percentage of lungs are appropriate for harvest in brain-dead patients, because many patients' lungs do not meet the criteria with unacceptable oxygen challenge test results. Patients with proper test results may fail to donate lungs due to pulmonary aspiration. More aggressive care of the patients may have an important role in keeping them in good condition and helping to preserve the organs for harvest. For this purpose, further training of intensive care unit staff and physicians are among the suggested steps to enhance the quality of care, which in turn can maximize the lung harvest rate.