Acetaldehyde is a toxic substance common to heavy drinking of alcohol and heavy smoking of cigarettes. It has been implicated thereby in diseases of the cardiovascular, respiratory, and central nervous systems. Protection against acetaldehyde toxicity (i.e. anesthesia and lethality) was studied in rats by oral intubation of test compounds 30-45 minutes prior to oral intubation of a standardized oral LD 90 dose (18 millimoles/kilogram) of acetaldehyde. Animals were monitored for anesthesia (loss of righting reflexes) and lethality for 72 hours. A total of 18 compounds was tested. L-ascorbic acid at 2 millimoles/kilogram (mM/kg) showed moderate protection against anesthesia and marked protection against lethality. Greatest protection against anesthesia and lethality was obtained at 2 m M/kg with each of the following: L-cysteine, N-acetyl-L-cysteine, thiamin-HCl, sodium metabisulfite, and L-cysteic acid. A combination of L-ascorbic acid with L-cysteine, and thiamin-HCl at reduced dose levels (2.0, 1.0 and 0.3 mM/kg, respectively) gave virtually complete protection. A detailed literature review is presented of the rationale and significance of these findings. Our findings could point the way to a possible build-up of natural protection against the chronic body insult of acetaldehyde arising from heavy drinking of alcohol and heavy smoking of cigarettes.

The ratio of toxic dose-protective dose of the fi~st two compounds warrants further study of them in combination with thiamin as possible protective agents against the chronic toxicity of acetaldehyde associated with heavy ethanol intake and heavy smoking.

The bacterial growth factor, tentatively called strepogenin, which stimulates the growth of a variety of bacteria, has been found in partial hydrolysates of vitamin-free casein.* It has therefore seemed advisable to examine several purified proteins for their ability to yield the factor on partial hydrolysis. Since Wright and Skeggsb have reported strepogenin-like activity for enzymic digests of casein, we have tested such preparations and found them to be more active than the partial hydrolysates prepared with dilute acid as described from this L a b~r a t o r y .~ Therefore, proteins to be examined were treated with trypsin rather than with acid.Tryptic digests of many proteins were found to be much richer sources of the growth factor than was the liver extract previously used as a starting point for purification. Most of these proteins were highly purified, and had been recrystallized repeatedly, All proteins, however, did not yield strepogenin activity when trypsinized. For example, dialyzed egg white, a m d e proteinaceous material, proved to be almost inactive, while crystalline proteins such as insulin and trypsinogen gave rise to activity far greater than that of liver extracts.The rate of liberation of strepogenin by the action of trypsin varied with different proteins. Maximal activity was obtained with digestion periods of twenty hours or less. In the case of casein, more strepogenin was released by trypsin than by pepsin.Since tryptic digests of certain proteins were richer in the growth factor than sources previously examined, these digests have been used as starting points for the purification of strepogenin. Several schemes for concentration of the sub? stance have been tested, and a few will be outlined in the experimental section. Some properties of the active agent which shed light on its chemical nature also will be included. ExperimentalMethods.-The strepogenin assays were performed with the aid of Lactobacillus casei according to the method described earlier.* It is necessary to emphasize, as indicated previously, that a small inoculum was used in this test, since with larger seedIngs the entire effect may be less well marked. In the preparation of the basal medium, it was found advisable to use the casein hydrolysates made with sulfuric acid as recommended rather than the hydrochloric acid hydrolysates commercially available. In the case of the sulfuric acid procedure, traces of strepogenin which survived the acid hydrolysis were removed by the barium (1) An abstract of this paper was published: Woolley and Sprince.(2) Fellow of The Xutrition Foundation, Inc. (3) With the technical assistance of B. Bailey and M. L. Collyer. (4) Sprince and Woolley, J . E x p . M e d . , 80, 213 (1944). ( 5 ) Wright and Skegns, J, Bncl., 48, 117 (1944). Fcdnation Proceedings, 4, 164 (10433.sulfate,' which was used to rid the solution of sulfate ion. When commercial hydrochloric acid hydrolysates were employed, the growth in the blank tubes was appreciable, but acceptable assays could nevertheless be obtained....