Harry G. Day

Effects of Acute Dietary Zinc Deficiency in the Rat

By means of a diet furnishing about 7 μg of Zn per rat daily, studies at the University of Wisconsin 1-4 have convincingly demonstrated the indispensability of Zn in the nutrition of rats, although the Zn-deficient diet permitted the experimental rats to gain about 8 g per rat weekly during the 10 week period on the diet. 4 The findings have invalidated the conclusion from our laboratory 5 several years ago that the element probably is not a dietary essential. We have recently prepared a diet furnishing not more than 2 to 4 μg of Zn per rat daily. Young rats restricted to it quickly developed extreme degrees of deficiency. Because the studies have been temporarily interrupted, owing to the transfer of one of us (H.G.D.) to another laboratory, we have decided to make a preliminary report on the work at this time. Diet. The diet was : casein hydrolysate (tryptic)† 15.00, egg white (cooked) 3.00, sucrose 66.29, salts 5.71, butter fat 10.00, and Oleum Percomorphum 50%, 2 drops per 100 g diet (approximately 2800 vitamin A units and 400 vitamin D units). Each rat was given a daily supplement containing the equivalent of 6.4 g liver, 40 μg of thiamin and 1.0 mg of choline. The liver concentrate,‡ dissolved in 6 volumes of water, was centrifuged. The supernatant solution was transferred to a Pyrex glass separatory funnel and the pH was adjusted to about 6. The solution was extracted repeatedly with dithizone (diphenyl thiocarbazone) dissolved in CC14. When no more Zn could be removed Zn-free dilute HC1 was added until the pH was about 4. The excess of dithizone was removed with redistilled CC14.

Effect of Ether Peroxides in Wheat Germ Oil on Production of Tumors in Rats

Rowntree and associates 1 have reported a high incidence of abdominal sarcoma in Wistar rats, as well as albino rats from the Buffalo and Yale strains, when fed crude wheat germ oil prepared by ether extraction. Great variability occurred in the rate of tumor production. In rats given 1 cc of oil daily tumors appeared in about 100 to 200 days; with 4 cc daily the average was about 54 days. The nature of the neoplastic agent has not been determined but since it appears to be absent from refined ether-extracted wheat germ oil, and wheat germ oils not obtained by means of ether, it is possible that the factor is produced by some action of ether on wheat germ. Owing to the tendency of unsaturated fatty compounds to undergo oxidation while in contact with ether containing peroxides 2 it appeared to us that the neoplastic agent might have arisen through the action of such peroxides, formed in the extraction of wheat germ with ether, although the latter was reported to be peroxide-free before it was used. We have tested this hypothesis as follows: Two volumes of C. P. peroxide-free anhydrous ether were added to one volume of fresh cold pressed wheat germ oil∗ in a glass flask fitted with a condenser. This oil was aerated seven hours by means of a slow current of air drawn through H2SO4 and glass wool. The mixture was allowed to remain in the flask at room temperature for 36 hours, without protection from light, after which most of the ether was removed by distillation at atmospheric pressure. The mixture was then placed in an evaporating dish and heated on a water bath for 2 to 3 hours, with occasional stirring to remove most of the ether that remained.

Biotin Deficiency in Rats Fed Purified Diets Containing Succinylsul-fathiazole and p-Aminobenzoic Acid.

Summary Biotin deficiency occurs in rats fed a purified diet containing sulfasuxidine and p-aminobenzoic acid. Growth appears to be a sensitive indicator of biotin deficiency in the rat.

Nicotinic Acid and Pantothenic Acid Content of Sunflower Seed Meal and Some Oil Seed Products.

Summary Sunflower seed meal is an excellent source of nicotinic acid. The content of pantothenic acid is equal or superior to that of soybean meal, wheat germ or corn, germ.

Influence of Pantothenic Acid Deficiency on Resistance of Mice and Rats to Experimental Pneumococcal Infection.

Summary A study of the resistance to the intraperitoneal injection of Type I pneumococci of 39 rats showing pantothenic acid deficiency in contrast to 36 controls fed pantothenic acid failed to reveal a significant change in the susceptibility of the experimental group. Similarly, no marked change in susceptibility was observed in 175 mice showing pantothenic acid deficiency in contrast to the survival percentage of 141 controls receiving the vitamin (normal animals). However, the difference is great enough to warrant the conclusion that acute pantothenic acid deficiency in mice may slightly increase the resistance to Type I pneumococcus. Certainly the results give no indication of decreased resistance to this organism in pantothenic acid deficiency.

Effect of Cecectomy and Succinylsulfathiazole on Vitamin K Synthesis.

Great interest is centered on the synthesis of essential nutrients by microörganisms of the digestive tract. 1 , 2 , 3 , 4 , 5 , 6 The cecum, aptly referred to as a “fermentation vat,” 6 is generally regarded as the principal site of this important function in the rat. Although quite a few reports have been made concerning the inhibitory effects of certain sulfonamides on the enteric synthesis of various vitamins very little experimental work has been done on the role of the cecum as a favorable site for such activity. The latter studies have been concerned only with the synthesis of B-complex vitamins 7 , 8 , 9 and the utilization of phytin phosphorus. 10 During the past year our investigation of factors affecting vitamin K synthesis in the intestinal tract 11 has included observations on cecectomized rats. The timeliness of certain of our findings prompts this short communication. Stock rats about 35 days old were started on a vitamin K-free diet of the following composition: casein (Smaco, vitamin-free) 18, glucose (Cerelose) 66, salt mixture 4, etherextracted brewers yeast 7, corn oil 3, cod liver oil 2, and choline chloride 0.04. After one week these animals were cecectomized and two days after the operation succinylsulfathiazole was added to the vitamin K-free diet at a level of 1% replacing an equal amount of glucose. Four weeks after cecectomy determination of the plasma prothrombin clotting time was started at biweekly intervals using a modification of Quicks method. 12 The blood was obtained by cardiac puncture under ether anesthesia. Severe hypoprothrombinemia occurred in 14 out of 17 cecectomized animals fed the vitamin K-free diet containing succinylsuflathiazole. Within 3 months nearly all had died from hemorrhage due to severe hypoprothrombinemia. Seven to severe hypoprothrombinemia. Seven out of 9 littermates cecectomized at the same time and fed the diet without succinylsulfathiazole had normal prothrombin clotting times. The remaining 2 showed only a slight increase in prothromibin time. Similarly, unoperated (not cecectomized) rats fed the vitamin K-free diet containing succinylsulfathiazole had only an occasional and very mild hypoprothrombinemia.

E. V. McCollum and Public Understanding of Foods and Nutrition

A historical perspective on the work of E. V. McCollum, a pioneer in nutrition education.