20
LEROY C. STEVENS
teratoid tumors in the testes of presumably noninbred white mice injected with a mixture of toxic substances and testosterone. Thus trauma,
coupled with the administration of hormones, has been shown to initiate
teratocarcinogenesis in the fowl, and according to Bresler (1959, 1964),
in the mouse. Other investigators (Willis, 1934; Guthrie, 1956; Stevens
and Mackensen, 1961, and evidence presented below) have attempted to
obtain teratomas or seminomas in mice and rats by several means, but
with negative results.
2. Position and Laterality Influences
It is well documented that the cryptorchid testis is more likely to
undergo malignant transformation than the normal scrotal testis in
man (Gilbert and Hamilton, 1940; Lewis, 1949; Willis, 1951; Dixon and
Moore, 1952; Patton et al, 1960).
The growth and differentiation of experimentally induced teratomas
of strain 129 mice (to be discussed below) is markedly influenced by
the site in which they develop. In the spleen, the tumors are small and
composed mostly of adult neural tissue (Stevens, 1964). On the other
hand, in the testis, they are large and are composed of many kinds of
tissues, like spontaneous teratomas in these mice. It appears that the
spleen provides a less favorable environment for the growth of these
cells during early stages of development of the tumors. Alternatively,
the splenic environment may promote the differentiation of the embryonal stem cells of these tumors.
Human teratomas of the ovary and testis occur with a greater frequency on the right than on the left side (Willis, 1948). Peterson et al
(1955), however, concluded that ovarian teratomas do not show a
laterality preference. About 70% of the teratomas of strain 129 mice
occur in the left testis (Stevens and Mackensen, 1961). It is difficult to
understand why laterality should influence teratocarcinogenesis. Delicate
local environmental influences must play a role.
3. Maternal Influence
In addition to local environmental influences, there is a maternal influence on teratocarcinogenesis in strain 129 mice (Stevens and Mackensen,
1961). The incidence of teratomas in males of second and later litters
is approximately twice as high as in males of first litters. There is also
evidence that young mothers "protect" first-litter offspring from
teratocarcinogenesis.
Conclusion. The susceptibility to teratocarcinogenesis in mice is the
result of the action of a single gene. The penetrance of this gene is
modified in both positive (Sl
J
) and negative (A
y
) directions by other
genes. Local environmental influences such as cryptorchidism and later-
LEROY C. STEVENS
teratoid tumors in the testes of presumably noninbred white mice injected with a mixture of toxic substances and testosterone. Thus trauma,
coupled with the administration of hormones, has been shown to initiate
teratocarcinogenesis in the fowl, and according to Bresler (1959, 1964),
in the mouse. Other investigators (Willis, 1934; Guthrie, 1956; Stevens
and Mackensen, 1961, and evidence presented below) have attempted to
obtain teratomas or seminomas in mice and rats by several means, but
with negative results.
2. Position and Laterality Influences
It is well documented that the cryptorchid testis is more likely to
undergo malignant transformation than the normal scrotal testis in
man (Gilbert and Hamilton, 1940; Lewis, 1949; Willis, 1951; Dixon and
Moore, 1952; Patton et al, 1960).
The growth and differentiation of experimentally induced teratomas
of strain 129 mice (to be discussed below) is markedly influenced by
the site in which they develop. In the spleen, the tumors are small and
composed mostly of adult neural tissue (Stevens, 1964). On the other
hand, in the testis, they are large and are composed of many kinds of
tissues, like spontaneous teratomas in these mice. It appears that the
spleen provides a less favorable environment for the growth of these
cells during early stages of development of the tumors. Alternatively,
the splenic environment may promote the differentiation of the embryonal stem cells of these tumors.
Human teratomas of the ovary and testis occur with a greater frequency on the right than on the left side (Willis, 1948). Peterson et al
(1955), however, concluded that ovarian teratomas do not show a
laterality preference. About 70% of the teratomas of strain 129 mice
occur in the left testis (Stevens and Mackensen, 1961). It is difficult to
understand why laterality should influence teratocarcinogenesis. Delicate
local environmental influences must play a role.
3. Maternal Influence
In addition to local environmental influences, there is a maternal influence on teratocarcinogenesis in strain 129 mice (Stevens and Mackensen,
1961). The incidence of teratomas in males of second and later litters
is approximately twice as high as in males of first litters. There is also
evidence that young mothers "protect" first-litter offspring from
teratocarcinogenesis.
Conclusion. The susceptibility to teratocarcinogenesis in mice is the
result of the action of a single gene. The penetrance of this gene is
modified in both positive (Sl
J
) and negative (A
y
) directions by other
genes. Local environmental influences such as cryptorchidism and later-