Direct Chemical Evidence Research Articles

Studies on the Eczematous Sensitization: IV. Sensitization to Metadinitrobenzene and Its Relation to 2:4 Dinitrochlorobenzene

In the study of sensitizations to simple chemicals, there are two somewhat ^ related chemical problems. One is the nature of the union between the sensitizing chemical and the tissues of the host in order to engender the eczematous sensitization, and the other is in what chemical respects can a substance that is capable of evoking a reaction in the already sensitized animal deviate from the parent sensitizing compound? It has been reasonably well shown, originally by v Landsteiner (1) and subsequently confirmed by others, that simple chemical compounds which are capable of inducing the eczematous variety of the delayed type of allergic sensitization enter into some sort of union with the tissues of the host. The simplest hypothesis is that a protein conjugate is made. There seems to be direct chemical evidence for this type of union with certain classes of compounds, such as substituted nitro- and halo-benzenes, especially the di-y nitrophenyls. Such a union may not be true for all substances which yield an eczematous sensitization, e.g., nickel, for, as Gell (2) states: Many chemical compounds which act as sensitizers have one general feature in common: they are capable of reacting with a group or groups in the molecule of a protein to form a conjugate. A second type of sensitizer is not able K itself to combine with protein, but may be metabolized in the body to a deriva-tive possessing such powers of combination. There may be a third category of > sensitizers which do not react chemically but form strong adsorption complexes with protein. In any case the conjugate or adsorption complex so formed will > become antigenically distinct from the parent protein, and if the sensitizer gains access to the tissues of an animal the proteins of the latter may be ren- * dered antigenic.

The Effect of 1470A Irradiation of Nitrogen-Hydrogen Mixtures and of Ammonia

The characteristics of a xenon resonance lamp were studied, using carbon dioxide as an actinometer, to determine the influence of the xenon pressure in the lamp on the intensity of the 1470A radiation. The xenon sensitized photosynthesis of ammonia was studied both in static and in flow systems. No ammonia could be detected. Some experiments on the photolysis of ammonia at 1470A are reported and discussed. The present work furnishes the first direct chemical evidence rejecting the value of 171.3 kcal per mole as the dissociation energy of nitrogen.

Formation of peroxide by actinomyces necrophorus on exposure to air in relation to anaerobic plate cultures

McLeod and Gordon 1 showed that the inhibitory substance which appeared in cultures of pneumococcus, and which had been called bactericidin by McLeod and Govenlock 2 was, in reality, hydrogen peroxide. A number of coccus forms, in addition to the pneumococcus, were shown to be peroxide formers when grown in the presence of air. Callow,3 investigating the question of whether or not the sensitiveness of anaerobic bacteria to air could be explained on the basis of peroxide formation coupled with a lack of ability to form catalase, found that all of the obligatory anaerobes with which she worked were devoid of catalase, but she was unable to obtain proof that any of them were capable of forming peroxide. McLeod and Gordon ' obtained a greenish zone in shake cultures of several anaerobes about 1/s inch beneath the surface in cooked blood agar. Since a similar color was obtained in cultures of several aerobic organisms which were known to be peroxide formers, and was not obtained in the case of any aerobe which did not produce peroxide, they regarded this phenomenon as an indication of peroxide formation. They did not obtain any direct chemical evidence of peroxide formation by anaerobes other than the action on blood, and the significance of this reaction may be open to question. Working on the hypothesis that it was the accumulation of peroxide in cultures of anaerobic organisms, made possible by a lack of catalase, which was responsible for failure of these organisms to grow in the presence of the free oxygen of the air, Avery and Morgan 5 showed