Electron microscopy of the normal and damaged pulmonary alveolus BRYAN CORRIN The electron microscopy of the normal alveolus is described with emphasis on function, particularly gas exchange, surfactant secretion, phagocytosis, and the metabolic processing of circulating vasoactive substances. The ultrastructural features of alveolar regeneration after cytotoxic injury are described together with the contribution of electron microscopy to our understanding of the pathology of the adult

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... ry distress syndrome. Electron microscopy of cancer of the lung BRIAN E. HEARD and ANN S. DEWAR The typing of lung tumours pathologically is based currently on appearances in paraffin sections observed by light microscopy, and a widely used classification is that of the World Health Organisation (1967). However, electron microscopy is bringing to light much new information on the structure of these tumours, which will have to be incorporated in future classifications. In this paper the authors describe some ultrastructural findings in their own series of lung tumours and discuss the impact of findings of this type on present concepts based on observations made over the years by light microscopy. Electron microscopy of muscular evaginations DONALD HEATH When smooth muscle cells shorten on collapse or constriction, bulbous evaginations project from their surface in the gaps between attachment points on the plasma membrane for myofilaments. On electron microscopy such evaginations have a clear cytoplasm devoid of organelles and myofilaments. In ultrastructural studies of pulmonary vascular pathology the observer who does not recognise such evaginations for what they are may be perplexed. Examples of this phenomenon induced by hypoxia and pyrrolizidine alkaloids are shown in the pulmonary trunk and pulmonary veins respectively. In a double-blind study, physicians made a thoracic diagnosis from computerised tomograms (EMI CT 5005-exposure time: 18 s) and from good standard radiographs. It is important to distinguish the true diagnostic value of this new method for thoracic lesions. 1 Degenerative pulmonary diseases The computerised tomogram is more spectacular than conventional radiology in pulmonary fibrosis and emphysema. 2 Infectious diseases In pneumonic consolidation or collapse, either lobar or segmental, one is able to visualise a nodular lesion amid a dense lesion. The contribution of the scanner is interesting in cases of mixed lesions involving a pleural component with a parenchymal lesion. 3 Neoplastic processes Small pulmonary tumours and an objective diagnosis in neoplastic lesions (adenocarcinoma, etc) are still difficult to establish. However, early pleural tumours are diagnosed much earlier, as are pleural effusions. 4 Metastatic les7ons Metastatic deposits that cannot be seen on conventional radiographs can be visualised on computerised tomograms (the vast majority of these are subpleural). The true indication is the formal exclusion of all neoplastic lesions when a surgical operation has to be done. 5 Mediastinal pathology The differentiation of various elements in the mediastinum is sometimes difficult except for large structures (eg, thymus, and mediastinal lymphoma). Computerised tomography is a very useful method in the study of the lung parenchymal and pleural pathology. However, in many cases, traditional radiology also permits an excellent approach to a similar problem. Computerised tomography in the pathology of the pleura and thoracic walls M. OSTEAUX and L. JEANMART In the thoracic field, where conventional radiology is efficient, it seems reasonable to limit computerised tomography (CT) to specific information. The following theoretical advantages of CT can be recognised: -Suppression of the superpositions without tomographical shadow, this being due to the point-topoint mathematical reconstruction of the picture -Great sensitivity to small density variations -Ability to measure the density and deduce the composition and eventually the nature of some components, either normal or due to a lesion 530 on 23 July 2018 by guest. Protected by copyright.