Mechanical and optical dynamic model of lung.

A multiscale, multiphysics model generates synthetic images of alveolar compression under spherical indentation at the visceral pleura of an inflated lung. A mechanical model connects the millimeter scale of an indenter tip to the behavior of alveoli, walls, and membrane at the micrometer scale. A finite-difference model of optical coherence tomography (OCT) generates the resulting images. Results show good agreement with the experiments performed using a unique indenter-OCT system. The images depict the physical result with the addition of refractive artifacts and speckle. Compression of the alveoli alters the refractive effects, which introduce systematic errors in the computation of alveolar volume. The complete computational model is useful to evaluate new proposed imaging instrumentation and to develop algorithms for obtaining quantitative data on deformation. Among the potential applications, a better understanding of recruitment of alveoli during inflation of a lung, obtained through a combination of models and imaging could lead to improvements in noninvasive treatment of atelectasis.

Rapid communication: protective effect of a nuclear factor kappaB inhibitor, pyrolidium dithiocarbamate, in the kidney of rats with nephrolithiasis induced by ethylene glycol.

PURPOSE: To study the protective effects of a selective nuclear factor kappa B (NF-kappaB) inhibitor, pyrolidium dithiocarbamate (PDTC), on ethylene glycol-induced crystal deposition in the renal tubules, renal toxicity, as well as inducible nitric oxide synthase (iNOS) and NF-kappaB activities in rat kidneys. MATERIALS AND METHODS: Rats were divided into three equal groups: control, ethylene glycol-treated (EG), and ethylene glycol + PDTC treated (EG+PDTC). Rats were sacrificed on day 7, 15, or 45, and tissue sections were evaluated under light and transmission electron microscopy for the presence and degree of crystal deposition and toxicity in the kidneys. The iNOS and NF-kappaB activity were evaluated immunohistochemically, with p65 being stained to define NF-kappaB activity. Crude extracts of the cortex were used to determine reduced glutathione (GSH), nitric oxide (NO), and malondialdehyde (MDA) concentrations. RESULTS: Crystal depositions were more evident in the proximal tubules on day 7 in the EG than in the other groups. Mild crystallization was observed on day 15, and severe crystallization and granulovacuolar epithelial-cell degeneration were observed on day 45. There was limited or no crystal formation in the EG+PDTC group and completely normal renal and tubular structures in the control group. Whereas ethylene glycol administration stimulated iNOS and NF-kappaB/p65 activity in renal tubules, PDTC inhibited it. Rats given only vehicle demonstrated no significant alterations. Hyperoxaluria, a marked increase in MDA and NO concentrations, and a decrease in GSH were observed in the EG group. CONCLUSION: This experiment has shown the role of transcription factors, NF-kappaB, and iNOS in ethylene glycol-induced crystal depositions in renal tubules.