Abstract
We have previously reported 1 that the application of 1% zinc sulphate to the olfactory mucosa of monkeys affords protection against poliomyelitis virus inoculated intranasally one or more months later. The basis of this protection is not yet understood. Nasal mucous membranes removed a week or more after treatment generally present a normal appearance. Recently, however, we have studied membranes removed several hours to several days after treatment with varying concentrations of zinc sulphate solution.
With a little experience it is possible to remove olfactory mucosa, olfactory nerve filaments and olfactory bulbs, of both sides, all in one piece. These have been embedded and sectioned tangentially. Such sections afford the orientation necessary for a satisfactory study of the olfactory mucosa and related structures and within limits allow comparison of treated and untreated sides.
Our observations show that by the end of the first day, there may be a marked acute inflammation, associated with some desquamation and necrosis of epithelial cells. Following treatment with 1.5% zinc sulphate solution, this change may be so marked that much of the olfactory mucosa loses its epithelium. The inflammatory reaction tends to subside quickly and is followed promptly by regeneration. By the end of the 2nd day denuded areas may be again covered with an epithelium consisting of flat or cuboid cells with many cells showing mitosis. By the end of the 3rd, 4th or 5th day the epithelial surface again appears normal, except for some disorder in the arrangement of the cells and for a few scattered collections of PMN cells.
It is generally held that destroyed nerve cells are not restored. We are, however, not aware of any observations proving that this holds also for olfactory cells. Should the protection induced in monkeys by zinc sulphate be the result of a. destruction of olfactory cells and not the result merely of an injury or chemical change in the dendrites of the olfactory neurons, it would then seem to follow that these structures are in reality regenerated in some way. This statement is justified in part on the ground that the majority of treated resistant monkeys become susceptible again in 2 to 4 months. Either the protection is not associated with a complete destruction of olfactory cells or certain cells in the olfactory area are differentiated into cells capable of forming axons and dendrites and of eventually restoring function. Such a provision does not seem entirely unlikely in a structure which is probably not altogether free of the risk of naturally induced injuries.
Get full access to this article
View all access options for this article.