Pulmonary hypertension is associated with the increased expression of endothelin-1 in vascular endothelial cells, suggesting that the local production of endothelin-1 may contribute to the vascular abnormalities associated with this disorder.

K E Y W O R D S . Cavalieri estimator, cycloid test system, fluid displacement, lung volume, pleural surface area, point counting, rabbit lung, stereology, stratification, systematic sampling, vertical sections. S U M M A R YA practical methodology is proposed for the stereological analysis of lung and other organs using recently developed unbiased procedures. This study concentrates on the unbiased estimation of lung volume using Cavalieri's principle compared with the fluid displacement method and measurement of pleural surface area using vertical sections. Furthermore, the proposed design, in addition to the sampling of extensive slices for the initial steps, also allows sampling of vertical sections for light and electron-microscopical stereology.The procedures are described in detail by reference to biological data from the right lungs of four rabbits. We found excellent agreement between estimates of lung volume measured with Cavalieri's principle and those measured by fluid displacement. Pertinent details of the statistical analysis of the sources of variation (namely biological, systematic sectioning and point-counting variation) are given in an appendix.

Idiopathic pulmonary fibrosis (IPF) is characterized by an alveolitis with epithelial and endothelial damage progressing to fibrosis. Numerous mediators have been implicated in this complex process. Studies in humans have shown that endothelin-1 (ET-1), a vasoconstrictor and mitogenic peptide, is a mediator in IPF. To determine the role of ET-1 and endothelin-converting enzyme (ECE)-1 and the effect of Bosentan, an ET receptor antagonist, in an animal model of IPF, we studied three groups of rats (n = 6 each): Group 1, control, received saline; Group 2, fibrosis, received 1.5 U bleomycin intratracheally; Group 3, fibrosis-Bosentan treated, received bleomycin and Bosentan daily by gavage. After 28 d, right upper lobes were fixed for immunohistochemistry (IHC) and sections were stained with antisera to ET-1 and ECE-1 and graded semiquantitatively. Sections from left lungs were embedded in paraffin and stained for light microscopic morphometry to quantitate the fibrosis. By IHC, we found increased ET-1 immunoreactivity (ir) in airway epithelium and inflammatory cells, and ECE-1-ir in airway epithelium, type II pneumocytes and endothelial cells (p < 0.05). By morphometry, the volume fraction (Vv) of connective tissue (CT) increased and the Vv of air decreased in the fibrosis group compared with that in the control group. Bosentan reduced the Vv of CT and increased the Vv of air compared with that in the fibrosis group (p < 0.05). These results indicate that ET-1 is involved in the pathogenesis of pulmonary fibrosis in the rodent model and that blockage of its receptors reduces the fibrosis.

Without doubt, the benefits of treatment of Hodgkin's disease outweigh the risk of a subsequent malignancy, but data on the carcinogenic effects of radiation and drugs beyond 10 years after treatment continue to be sparse, and future analyses should be directed at long-term survivors.