Document yk83NR7b5n1wOoDBadLmx5923

796 OCCUPATIONAL TUMORS AND ALLIED DISEASES thesis (Brock), Kogl connected this phenomenon with the autocatalytical production in vivo of an altered protease (cathepsin), which is generated in the tumor tissue endogenously in a fashion comparable to the exogenous develop ment of tumor viruses. In further elaborating on the possible biological mean ing of the alleged stereochemical protein abnormalities of tumor tissue, Kogl stated that the length of the latency period depended upon the rate at which d-aminoacids are incorporated into the cellular proteins. When the cellular con tents of d-aminoacids surpasses a critical level, a fundamental change in the cellular character occurs, according to Kogl. The existing morphological differ ences between cancers of various types were attributed by Kogl to variations in the number and character of the d-aminoacids composing the protein matter of different neoplasms. Carcinomas were said to be distinguished from sarcomas by a higher content of d-aminoacids, providing a chemical substantiation of the different structural nature and biological behavior of these two types of malignant growths. The chemical observations on tumor tissue made by Kogl were confirmed by Arnow and Opsahl; and White and White, but could not be substantiated by Chibnall, Rees, Tristram, Williams, and Boyland} Graff, Chargaff and Lipmann} Behrens, Kabat and Burk. The latter group of investigators pointed out that the uniformity and low order of d-aminoacids observed in a variety of hydrolysates examined, whether from benign or malignant tumors, normal tissues, or proteins, showed that malignancy is, as a rule, not specifi cally characterized by the presence of aminoacids of unnatural (d-) configu ration. Klinke maintained, from his investigations on the d-aminoacid content of the rabbit myxoma, a virus propagated tumor, that d-aminoacids are not cancer specific in etiologic respects, but reflect merely local or general cellular or tissue, disturbances. While the contradictory character of the in vitro studies on the d-aminoacid content of cancers does not permit at the present time a definite decision con cerning the validity of Kogl's claims from a chemical viewpoint, the specula tive interpretations as to the biological significance of such stereochemical ab normalities, if actually existing, are unwarranted to a large extent by the evi dence presented and are contrary to certain well-established facts. In connection with the theories of Waldschmidt-Leitz and Voegtlin it was mentioned that infiltrative and destructive growth is not a quality specific for and limited to malignant cells, as it is commonly observed with chronic, inflammatory, epi thelial hyperplasias, endometrioses, and glioses, and can be reproduced in tissue cultures containing two types of tissue by varying the growth rate through changes produced in the environmental nutritive medium. Apart from this ob jection it must be doubted seriously that proteolytic enzymes are unable to hydrolyze tumor protein, as it is an every day experience to see cancerous necroses gradually absorbed by the invasion of the various phagocytic elements