Elastin is known to occur in the lung parenchyma and pleura as well as in the pulmonary vessels, but no detailed studies of this elastin's linkage between them have been done in three dimensions. For many years we have known that there is abundant elastin in the mammalian lungs, which may be associated with etiology of causing emphysema. We have developed selective casting methods to allow us to determine the location where elastin is found morphologically. The method involves casting either the vasculature via the right ventricle, or the airways via the trachea in the air sacs. Studies of the vasculature were done with the lung inflated to 80% of the vital capacity. The casted lungs were then put in 0.1 N NaOH at 75 degrees C for 48 hours, turning them frequently. THis method removed all non-elastin tissues. The scanning electron microscopy (SEM) was used to reveal the three dimensional pictures of elastin structures from both lung parenchyma and pulmonary vessels. Elastin was seen as fenestrated sheets and some fibers in both the vessels and the airways. Elastin in the two different locations was often interconnected. Studies on 6 dogs, 8 rabbits, and 2 pigs showed no significant species difference at the level of resolution of the SEM, which was used to study the specimens after they had been freeze-dried.
Animal ; Blood Vessels/metabolism/ultrastructure ; Corrosion Casting ; Dogs ; Elastin/*ultrastructure ; Lung/blood supply/*metabolism ; Microscopy, Electron, Scanning ; Pulmonary Alveoli/metabolism/ultrastructure ; Rabbits ; Swine

The architectural changes which occur in the capillaries are difficult to illustrate without a three-dimensional tool, such as scanning electron microscopy. Therefore, a scanning electron microscopic study was occasionally undertaken to show the capillary changes of lung fibrosis. Fibrosis was induced in twenty rats by an intratracheal injection of bleomycin. After 30 days the rats were sacrificed, and light microscopy and scanning electron microscopy were performed. The vascular trees of both lungs were cast with methacrylate. Light microscopically, the pulmonary fibrosis was patchy and inflammatory cell infiltration was rather sparse. Scanning electron microscopically, the intercapillary spaces became wider; and some capillaries revealed large irregular dilatation. The pleural and alveolar capillaries were variably dilated. The pleural capillary diameter was increased (P = 0.06), and the capillary plexus diameter was decreased (P = 0.00). Distance between the capillary branches of the pleural surface was increased (P = 0.06). The appearance of irregularly shaped capillaries, an increase in diameter with variable dilatation of alveolar capillary rings and a decrease in branching between the capillaries, resulting in a loss of surface area are the main scanning electron microscopic findings of the remodeling which occurs pulmonary capillaries in bleomycin-induced pulmonary fibrosis.
Animals ; *Bleomycin ; Capillaries/pathology/*ultrastructure ; Microscopy, Electron, Scanning ; Pulmonary Alveoli/*blood supply/ultrastructure ; Pulmonary Fibrosis/chemically induced/*pathology ; Rats ; Rats, Inbred Strains