V OTHER METABOLIC FEATURES 915 



several stages of the oxidative sequence but not to the stage of the formation of 

 the melanin complex. New developments may be expected in the near future 

 that will clarify the entire mechanism of melanization as well as the fvmction of the 

 tyrosinase system in the metabolism of malignant melanoma. 



Shapiro and associates (1956) have continued their investigations on the quan- 

 titative differences in various components of the tumor and host. Total riboflavin, 

 flavin adenine dinucleotide, mononucleotide and free riboflavin were measured in 

 the adenocarcinoma and host tissues of C57 mice. Riboflavin was lower in tumor 

 than any other tissue analyzed except muscle. This general pattern has been 

 observed with many of the vitamins in that the normal tissue concentrations will 

 cover a wide range while the values for tumor are usually near the lowest normal 

 values. This group of investigators (Shils et ai, 1956) measured the thiamine, 

 coenzyme A, riboflavin, pyridoxine in mammary adenocarcinoma and in several 

 normal tissues. Heart, kidney and tumor were all high in these components. The 

 tumor was relatively low but the in same general range as muscle, lung, testes, 

 brain, intestine and stomach. 



(b) Alinerals 



Several minerals, calcium, copper, iron and zinc are present in lower concentra- 

 tion in methylcholanthrene induced carcinoma than in normal mouse skin (Cow- 

 dry, 1953). Much of the older literature relative to the chemical composition of 

 tumor has been reviewed by Greenstein (1954, Chapter 8). DeLong et at. (1950) 

 have discussed the significance of the generally low calcium and high potassium 

 contents in neoplastic tissues. Spectrographic methods were developed by Smith 

 et al. (1953) for determining the mineral content of normal human tissues and 

 neoplasms. 



A large number of human neoplasms were analyzed by Waterhouse et al. ( 1 955) 

 for water, nitrogen and electrolyte content. A high total water content was ob- 

 served while the total nitrogen, based on a dry weight basis, was in the normal 

 tissue range. A high intracellular concentration of potassium and phosphorus was 

 noted in most tumors. Injections of zinc salts, according to Chahovitch (1955) 

 accumulated in sarcoma tissue and also accelerated the rate of growth of this 

 tumor. Several trace elements were studied spectrographically in the livers of 

 patients with cancer. Iron, zinc, chromium and cobalt were elevated in the liver 

 liver in instances of acute lymphatic leukemia with hepatic involvement (Olson 

 et al., 1954). 



(c) Other metabolic features 



The highest levels of acetyl choline were found in the peripheral parts of tumors. 

 The level of this component was roughly proportional to mitotic activity in the 

 tumors (Svec and Hlavayova, 1953). Furth et al. (1953) have obtained transplant- 

 able pituitary tumors capable of secreting ACTH. Crystalline protoporphyrin 

 was obtained from an extract of chloroma (Schulz and Schwartz, 1956). Adminis- 

 tration of glycine-2-''*C resulted in a greater uptake of ^'*C on porphyrin of the 

 tumor than in hemes of the non-tumorous tissue, indicating the de novo synthesis 

 of porphyrin by this neoplasm. 



Literature p. gig 



