Episodes Of Destruction Research Articles

Development of a Canine Model of Experimental Emphysema by Intratracheal Instillation of Elastase

The pathogenesis of emphysema is postulated to be mediated primarily by endogenous elastolytic enzymes. This theory suggests proteolysis of pulmonary tissue occurs when active pulmonary phagocytes release elastolytic enzymes in quantities which exceed the inhibitory capacity of the locally available antiproteases, either because of extensive enzyme release or because of congenital alpha1-antitrypsin deficiency. The destructive episodes occur over time at diffuse locations until identifiable functional alterations result and at that point clinical emphysema can be identified.

Effect of complement fixation on the release of lysosomal enzymes from rabbit alveolar macrophages.

Macrophage lysosomal enzymes that have specificities for substrates found in mammalian tissue may contribute to the tissue damage observed in chronic inflammatory diseases. Although a variety of agents that stimulate the release of hydrolases from peritoneal macrophages have been identified, little work has been done to establish the conditions and specific stimuli responsible for enzyme release by alveolar macrophages (AM). To assess the effect of phagocytosis by AM on the release phenomenon, hydrolytic enzymes normally sequestered in AM lysosomes were quantified in the supernatant fluids of phagocytosing and non-phagocytosing AM monolayers in both the presence and absence of serum. Maximum release occurred under conditions known to favor complement fixation by the classical or alternative pathways. Thermal destruction or immune fixation of serum complement before use in culture reduced the magnitude of release to that observed in cultures incubated in the complete absence of serum. Phagocytosis was not essential for release, since cells exposed to particles but treated with a known inhibitor of phagocytosis (cytochalasin B) still showed maximal release in the presence of fresh serum. These data are interpreted to indicate that a heat-labile component of serum, probably a by-product of complement fixation, was primarily responsible for the hydrolase release by AM. On the basis of these findings, individuals suffering from chronic pulmonary disease may suffer acute episodes of lung destruction from endogenous AM enzymes upon the inhalation of materials capable of fixing complement.

Distribution of Lunar craters according to morphology from Ranger VIII and IX photographs

A classification of the craters photographed by the Ranger VIII and IX missions into four categories according to relative sharpness shows that at diameters of 100 meters, the predominant craters have broad rims and low depth-diameter ratios and are partly covered with smaller craters which generally have sharper rims and higher depth-diameter ratios but include all classes. If competing processes of crater formation and destruction are responsible for the mix of crater types observed, an abrupt increase in the proportion of sharp craters suggests an intense episode of crater destruction to produce a smoothed surface that was subsequently recratered. Data comparable to those presented can readily be obtained from Lunar Orbiter photographs to determine if an increase in the proportion of sharp craters is present over more extensive areas and to test various cratering histories that may account for it.

Official Policies and Economic Prospects

T HE present economic situation is controlled by three groups of forces: natural revival forces, official recovery stimulants, and the reform program. It is not my purpose to dwell upon classification niceties, but brief attention to such points will serve as a helpful beginning. We might instructively classify the items of the official economic program under three heads -relief, recovery, and reform. In such a classification the relief items, or those concerned primarily with relief, would bulk very large. A two-category classification, which merges relief with the others, brings out a most important clash of opinion as to public policy: the clash concerning the wisdom of jeopardizing recovery in order to achieve reform. Earlier, indeed, a clash of opinion appeared on another point: should we attempt a stimulated recovery, or let nature take its course? It is doubtful if, by the spring of I933, any considerable body of opinion favored entire reliance upon so-called natural forces for a cure of the depression. Even the outgoing Federal Administration had taken energetic actions, in limited areas, to facilitate or promote recovery. But a very substantial body of opinion not very popular among the mass, and particularly the suffering mass, of our people clearly favored a main reliance upon these natural forces. According to this opinion a more or less natural recovery had already begun in the summer of I932; the I933 bank crisis was a final, and perhaps avoidable, destructive episode in the readjustments incident to the depression; the reopening of the banks and the other confidence-restoring incidents at that time provided the essential impulse toward a vigorous upward movement; and government actions might well be confined largely to granting specific relief in certain areas where hardship was so acute as to impede general recovery. Under existing political auspices this issue as to whether natural forces should be relied upon is largely academic: the present Administration from the start insisted on action. Once that decision had been made and it had undoubtedly been reached long before March I933 it was certain that official policy would aim at stimulated, rather than natural, recovery. Even after this basic decision was made and became known, some critics still urged that all stimulants should be withdrawn as promptly as possible, and that natural forces should be allowed to resume their functioning. This view, in its extreme form, has little chance of being heard under existing political conditions; but in its moderate form it is likely to have and is already having important influence upon public policy.