GENERAL ZOOLOGY 



entirely different result of deficiency of E vitamins in young rats and in rabbits 

 and guinea pigs is degeneration of skeletal muscle, or muscular dystrophy. 

 The E vitamins are chemically known as tocopherols and are available in 

 green leafy vegetables, whole wheat, and egg yolk. Up to the present time, 

 a requirement for tocopherols in human nutrition has not been established. 



Vitamin K, the antihemorrhagic vitamin, is involved in an unknown way 

 in the production of prothrombin in the liver and is, therefore, necessary for 

 the normal clotting of blood (p. 64). A dietary deficiency of this vitamin, 

 which is a naphtho-quinone, is unlikely since it has wide distribution in foods. 

 Good sources are green leafy vegetables, tomatoes, cheese, egg yolk, and liver. 

 In addition, bacteria normally present in man's digestive tract synthesize 

 vitamin K, which is then absorbed. Certain sulfa drugs and other intestinal 

 antiseptics may cause a deficiency by reducing the number of bacteria which 

 produce the vitamin. Also, if absorption is interfered with, deficiency may 

 result. In the absence of vitamin K, the amount of prothrombin in the blood 

 is reduced and clotting time is prolonged. A deficiency of vitamin K occurs 

 in newborn infants, since the intestine is sterile and the amount of the vita- 

 min supplied by the mother is small. Sometimes bleeding may be severe, 

 or even fatal. Some physicians routinely give supplementary vitamin K 

 to expectant mothers in order to prevent hemorrhagic episodes in the 

 newborn. 



The first water-soluble vitamin to be identified was named vitamin B. It was 

 soon realized that the effects attributed to vitamin B were related to a number 

 of different substances, all of which were in some way growth-promoting. In 

 other words, there was not a single B vitamin but, instead, what is referred 

 to as the B complex. We shall consider some of the better-understood com- 

 pounds in the complex, all of which are available in crystalline form. 



Thiamine, or vitamin Bj, was the first member of the B complex to be 

 identified. After its isolation from rice polishings, it was synthesized in 

 1936. Thiamine is fairly widely distributed in foods, especially in whole 

 grains, legumes, lean meat, and yeast; however, only small amounts are 

 present in any source. Thiamine deficiency is generally characterized by loss 

 of appetite and consequent malnutrition. Later, neurological symptoms and 

 dysfunction of the heart and other organs occur. It has been clearly shown 

 that thiamine pyrophosphate is involved in the cellular metabolism of carbo- 

 hydrate, functioning as a coenzyme called cocarboxylase (p. 36). 



Riboflavin, lactoflavin, vitamin B^ or G, is necessary for the growth of many 

 animals, including man, and for the preservation of health in the adult. This 

 vitamin occurs in yeast, milk, eggs, liver, and some vegetables. Riboflavin 

 deficiency in man is widespread and gives rise to soreness at the angles of the 

 mouth, inflammation of the tongue, and tissue damage in several parts of the 

 eye. The physiological role of riboflavin is correlated with its union with 

 phosphate to form flavin nucleotides which then combine with proteins. 

 These complex flavoprotein molecules have multiple functions in oxidative 

 metabolism as assistants to a number of enzymes (p. 37). 



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