Material model of lung parenchyma based on living precision-cut lung slice testing.

We describe a novel constitutive model of lung parenchyma, which can be used for continuum mechanics based predictive simulations. To develop this model, we experimentally determined the nonlinear material behavior of rat lung parenchyma. This was achieved via uni-axial tension tests on living precision-cut rat lung slices. The resulting force-displacement curves were then used as inputs for an inverse analysis. The Levenberg-Marquardt algorithm was utilized to optimize the material parameters of combinations and recombinations of established strain-energy density functions (SEFs). Comparing the best-fits of the tested SEFs we found Wpar = 4.1 kPa(I1-3)2 + 20.7 kPa(I1 - 3)3 + 4.1 kPa(-2 ln J + J2 - 1) to be the optimal constitutive model. This SEF consists of three summands: the first can be interpreted as the contribution of the elastin fibers and the ground substance, the second as the contribution of the collagen fibers while the third controls the volumetric change. The presented approach will help to model the behavior of the pulmonary parenchyma and to quantify the strains and stresses during ventilation.

Endoscopic features of intestinal smooth muscle tumor in a child with AIDS.

Intestinal leiomyosarcomas are exceedingly rare in immunologically intact children, except during infancy. While leiomyosarcomas account for less than 2% of all soft tissue tumors in childhood, they are the second most frequent malignancy in children with the acquired immunodeficiency syndrome (AIDS). In this cohort they are often located in unusual sites for primary soft tissue tumors. This report describes a young girl with advanced AIDS, referred for evaluation of abdominal pain, hematochezia, and wasting syndrome. Colonoscopy revealed two 1- to 2-cm submucosal nodules with central umbilication. Repeat colonoscopy 18 months later revealed no changes in these lesions. Biopsy revealed a submucosal spindle-cell lesion, with necrosis and cellular atypia. Initially it was characterized as a partially excised low-grade leiomyosarcoma. However, the final consensus diagnosis was smooth muscle tumor of uncertain malignant potential. Because of her advanced AIDS, there was no attempt at surgical resection or chemotherapy. Thirty-six months after initial referral, she remains alive without radiographic or clinical evidence of local extension or metastases. Additional data are required to determine the long-term outcome of these indolent submucosal tumors in the digestive tracts of children with AIDS.

[Epidermolysis bullosa atrophicans gravis. Report of a therapeutic trial with dapsone]. / Epidermolysis bullosa atrophicans gravis. Bericht über einen Therapieversuch mit Dapson.

A case of junctional epidermolysis bullosa (Herlitz) is reported. The patient has been treated with high doses of Dapson. The result is encouraging.