Cancer cell biology / edited by Takeo Nagayo, Wataru Mori.

Date:
[1980]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Cancer cell biology / edited by Takeo Nagayo, Wataru Mori. Source: Wellcome Collection.

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    Table I. Incidences of Teratomas in Three Subgroups of Fetal Testes from 129/S \-ter Hi-line Group of testes Quantity of PGC Proliferative period of PGC % testes with teratomas I a 2 b 3 C Normal Normal Reduced Normal Moderately extended Markedly extended 7 50 92 a Testes having 20 or less than 20 dividing PGC, from 29 fetuses with head length 8.2 to 8.6 mm. b Testes having more than 20 dividing PGC, from 15 fetuses with head length 8.2 to 8.6 mm. c Testes having an extremely reduced number of PGC, from 6 fetuses with head length 8.3 to 11.5 mm. testes having a normal number of PGC were divided into two groups corresponding to Groups 1 and 2 based on the level of dividing cell number. Table I summarizes the character of the three subgroups of testes and their tumor incidences. The incidences varied greatly among the subgroups. Group 3 testes always appeared bilaterally. Accordingly fetuses with Group 3 testes had a high tendency to have bilateral teratomas (5/6). Group 2 testes did not necessarily appear bilaterally. Fetuses having at least one Group 2 testis also showed a high incidence of bilateral teratomas (6/15). On the contrary fetuses having Group 1 testes rarely had bilateral teratomas (0/29). This is the first experiment that determined quantitatively the pattern of develop mental change in the proliferative activity of PGC in the testes of fetal mice. The mitotic index was 3 to 6% until late in the 13th day, and decreased precipitously. This pattern of change in PGC proliferation exactly paralleled the declining pattern of the susceptibility of fetal testes to experimental teratocarcinogenesis. PGC lose their sus ceptibility to teratocarcinogenesis as they lose their capacity to proliferate. By comparing the proliferative pattern of PGC in the subline with the highest incidence of teratomas to those of sublines with low incidences of the tumors, three unusual phenomena in the proliferative behavior of PGC were revealed in the subline with the highest incidence. Among these, a decrease in the total number of PGC ob served at the 13th day and extension of the proliferative period observed between the 13th day and 15th day were correlative to a high incidence of teratomas. It is possible that the extension of the proliferative period of PGC may enhance, in some way, the risk of conversion of PGC into teratomas. This experiment showed that the fetuses of strain 129/Sv-fer Hi-line are hetero geneous in respect to the character of the testes. The author recently found that some ovaries from Hi-line fetuses had a remarkably reduced number of PGC (unpublished data). Such abnormal ovaries occurred bilaterally as in the case of the testes. The cause of this heterogeneity has not yet been clarified. But the author now has a hypothesis explaining this heterogeneity. The mice strain, 129/S \-ter Hi-line might have a hidden recessive mutation (tentatively called ter ) which causes the abnormality in the fetal gonad. If male mice have bilateral teratomas, most of them become sterile (13). It is possible that the females with the abnormal ovaries may have some disadvantage in Comment