1942: Biochemistry

Nutrition and National Defense.

The National Nutritional Conference for Defense, first called into being by President Roosevelt in 1941, is now acting towards problems of nutrition in much the same way that the general army headquarters acts towards problems connected with the army.

Our problem is complicated by the fact that there is an acute labor shortage on the farms, and that much of our produce goes to the armed forces and to the Allied Nations. Despite such drawbacks, we easily remain the best-fed nation in the world. This applies particularly to our armed forces. Not only are their calorific needs taken into consideration, but the utmost care is taken to ensure biologically wholesome and esthetically attractive meals. The soldier in normal garrison life is allowed 4,200 calories and over 5,000 under combat conditions. The average civilian allowance is 3,000 calories.

The acute shipping shortage has resulted in the development of efficient methods for drying foods. These dried foods occupy anywhere from one-fifth to one-tenth the space occupied by the undried foods.

Vitamins.

The vitamin B complex now includes ten different substances. In addition to thiamin, riboflavin and niacin, we have pyridoxine, pantothenic acid, biotin, para-amino-benzoic acid, inositol, choline and folic acid. There is still some doubt about the last one; and Woolley has suggested that for the guinea pig, at least, there may be two or three more factors.

The 'enriched bread,' now so common in England, and becoming common in our country, is white bread 'enriched' by the addition of thiamin, niacin and iron. Sometimes, but not always, further additions of riboflavin, vitamin D and calcium are made. The white bread requires enrichment because it is made from flour which has been refined and has therefore lost some of its vitamins and minerals.

Perhaps the most sensational discovery in the field of vitamins during the past year has been the isolation and the study of the chemistry of biotin by Du Vigneaud. This biotin prevents the so-called 'egg-white injury.' It has been shown that when egg-white becomes a source of protein in the diet of rats, the animals develop a severe skin disease. This dermatitis has been traced to the presence of a protein in egg-white to which the name 'avidin' has been given. Apparently, biotin has the power of neutralizing the effects of avidin.

Biotin is a fairly complex organic substance containing not only the elements carbon, hydrogen and oxygen, but nitrogen and sulfur. It is an organic acid and part of its molecular make-up resembles the amino acid histidine, obtained from most proteins. The other part of its molecular make-up resembles thiophene, a sulfur compound long known to the organic chemist.

Food Requirements.

We now know that when we talk of 'protein requirements' we really refer to those structural units, the amino acids, which go to make up these proteins. In the past twenty years or so, much work has been done on the 'essential nature' of these various amino acids (of which there are some twenty odd). Which of the amino acids are absolutely indispensable for health and normal well being? Some ten of them are definitely in the class of indispensables.

However, practically all of such work has been done on the rat; and the question naturally arises whether what is true for the rat applies to other animals? A partial answer can already be given. The amino acid glycine, which is dispensable in so far as the rat is concerned is not dispensable in so far as the chick is concerned. A somewhat similar result has been obtained with the amino acid arginine.

These somewhat unexpected results make it clear that such knowledge obtained by using rats (or chicks) cannot necessarily be applied to man. To find out man's needs, man himself must be the subject; and such experiments are now being made.

Fluorine and Tooth Decay.

Fluorine is present in various tissues of the body, particularly in bone and teeth. It has been estimated that the normal bone contains from 0.01 to 0.03 per cent of fluorine; and dental enamel, 0.01 to 0.02 per cent.

Mottled enamel, a defect in teeth, has been attributed to the fluorine contained in the drinking water in certain sections of the country. The amount must be in excess of 2 parts per 1,000,000. Such teeth show chalky white patches, and the enamel is frequently pitted and corroded. Histological examination reveals imperfect calcification.

The startling claim has been made that a certain amount of fluorine in the water — somewhere in the neighborhood of 1.8 parts per 1,000,000, and therefore less than what would give rise to mottled enamel — protects against dental caries or tooth decay. When the drinking water contains but a trace of the element, caries is more prevalent. The suggestion has been made that when the enamel contains appreciable quantities of calcium fluoride, it becomes more resistant to acid attacks.

Blood Plasma and the War.

An outstanding success in medicine has been the discovery that blood plasma — and not necessarily whole blood, which would have to be 'typed' — can be used for emergency treatment of shock and hemorrhage.

The blood cells are separated from the plasma by sedimentation or centrifugation. The pooled plasma is preserved at 3° to 5° Centigrade.

Dried plasma has also come into much use. The fluid plasma is sprayed into a distilling flask maintained at reduced pressure and at a temperature not above 45° Centigrade. When needed, the dried plasma is mixed with glucose and sterile distilled water, and sulfathiazole is added as a preservative.

Genes and Viruses.

Stanley emphasizes the similarity of viruses (submicroscopic, infectious entities) and genes (factors governing hereditary traits). In size and in composition both resemble one another. Both reproduce within certain specific living cells. Both may undergo mutations — spontaneously or as a result of irradiation — changes which are reproduced in subsequent generations.

So far, unlike viruses, it has not been possible to isolate and study genes in vitro.