EXPERIMENTNAL STUDIES ON BRAIN TUMORS

Abstract

1. 10 to 16-day pregnant APG hamsters, new-born APG hamsters and pregnant Donryu rats (whose embryo length 25 to 32 mm) were killed, and the embryo brains as well as new-born hamsters' brains were removed aseptically. The brain fragmemts were pooled in a beaker with a small amount of saline solution and kept at 37°C until the material was ready for inoculation. 85 young adult APG hamsters (50 g in body weight) and 73 young adult Donryu rats (60 g in body weight) were used as the recipients of the transplantation of the brain tissue. The brain tissue was transferred by injection with a syringe into the right cerebral hemisphere of the recipients. As a result space taking lesions were produced intracerebrally in 56 APG hamsters and in 2 Donryu rats.2. Histological observations revealed that the produced lesions were made up of two large groups.In one group the lesions consisted of three germlayer components. (Teratoma-like lesion).In the other group the lesions consisted of well-developed nerve cells. (Gangliocytoma-like lesion).The incidence of teratoma-like lesion was 17 (15 in hamsters, 2 in rats) and that of gangliocytoma-like lesion was 41.Gangliocytoma-like lesions varied in size. They ranged from ones occupying the cerebral hemisphere to the small ones which could be recognized microscopically. Microscopic lesions were 10 including 5 with hydrocephalus.3. Host brains were removed and examined immediately and at intervals ranging from 3 to 27 days after the operation. It was found that the implanted tissue grew and differentiated until it formed a nodulous lesion. There were bones, cartilages and other tissue mixed in one case. It must be inferred that teratoma-like lesions were introduced as a contaminant due to the difficulty encountered in separating brain tissue from surrounding structures.4. One group of the animals was injected intramuscularly with carcinogen (20-methylcholanthrene). But there was no significant difference statistically in the number of lesions induced between the treated and non-treated animals. Nor any qualitative difference was revealed by histological observation.Several mother hamsters were killed after injection of H3-methylcholanthrene, and the radioactivity of their organs and embryo organs was counted by liquid scintillation counter. But the radioactivity was too weak to show that methylcholanthrene entered the embryonic brain. It may be said that in this experiment administration of carcinogenic agent did not play any significant role in forming nodulous lesions.5. 10 lesions (teratoma-like lesion 6, gangliocytoma-like lesion 4) produced by this method were implanted subcutaneously into the animals of the same species. Two of the implants grew slowly in subcutaneous tissue to form pea-size nodules. Their histological structures were both teratoma-like. Implants of gangliocytoma-like lesions produced no results.It is known from experiments of killing and examining hosts at regular intervals that gangliocytoma -like lesions come to full maturity in 3-4 weeks after implantation, and that they remain as malformations occupying the brain, which do not have true neoplastic character.6. This experiment suggests that congenital brain tumor of humans including gangliocytoma and teratoma is a space taking intracranial lesion which may grow from malformations.