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OBJECTIVES Primary spontaneous pneumothorax has long been explained as being without apparent cause. This paper deals with the effect of chest wall shape and explains how this may lead to the pathogenesis of primary spontaneous pneumothorax. METHODS Rib cage measurements were taken from chest radiographs in 12 male pneumothorax patients and 12 age-matched controls. Another group of 15 consecutive male thoracic computerised tomography (CT) were investigated using paramedian coronal and sagittal CT reconstructions to assess apical lung shape. A finite element analysis (FEA) model of a lung apex was constructed, including indentations for the first rib guided by CT scan data, to assess pleural stress. This model was tested using different anteroposterior diameter ratios, producing a range of thoracic indexes. RESULTS The pneumothorax patients had a taller chest (P = 0.03), wider transversely (P = 0.009) and flatter (P = 0.03) when compared with controls, resulting in a low thoracic index. Prominent rib indentations were found anteriorly and posteriorly on the lung surface, especially on the first rib on CT. FEA of the lung revealed significantly higher stress (×5–×10) in the apex than in the rest of the lung. This was accentuated (×4) in low thoracic index chests, resulting in 20-fold higher stress levels in their apex. CONCLUSIONS The FEA model demonstrates a 20-fold increase in pleural stress in the apex of chests with low thoracic index typical of spontaneous pneumothorax patients. Mild changes in thoracic index, as occurring in females or with aging, reduce pleural stress. Spontaneous pneumothorax occurring in young male adults may have a biomechanical cause. [ABSTRACT FROM AUTHOR]

Plants are an important source of several clinically useful anti-cancer agents. A volatile extract was obtained from Ricinus communis L. (Euphorbiaceae) leaves by standard hydrodistillation and subsequent extraction of the cohobated water in chloroform. GC-MS identified three monoterpenoids: 1,8-cineole, camphor and α-pinene, and a sesquiterpenoid: β-caryophyllene, as the main constituents. The leaf extract is cytotoxic to several human tumour cell lines in a dose-dependent fashion, with IC50 values ranging between 10-40 µg mL-1. Apoptosis was shown to be induced in SK-MEL-28 human melanoma cells at a concentration of 20 µg mL-1, as identified by means of morphological examination, nuclear staining and flow cytometric analysis of DNA content. Translocation of phosphatidyl serine to the cell membrane's external surface and loss of mitochondrial membrane potential were also detected. This study provides further insight into the potential use of mixtures of terpenoids as they occur in nature, as inducers of apoptosis in cancer cells. [ABSTRACT FROM AUTHOR]