634
ILSE L A S N I T Z K I
(1956) suggested that their effectiveness also depended on the presence
of pituitary hormones, as in hypophysectomized animals steroids only
produced enlargement of the ducts without lobular differentiation.
Lyons, Li and Johnson (1958) postulated a mechanism of mammarygland development in which the pituitary hormones exert an indirect
influence by controlling the function of most endocrine glands including that of the ovary and the adrenal.
Tissue culture experiments, in which the influence of various hormones on the development of the mouse mammary gland grown as
organ culture was investigated, demonstrated a direct effect of the
hormones on the tissue and showed that a combination of hormones
was necessary to achieve growth and differentiation of the immature
organ, and to maintain the structure and function of the adult gland.
The use of defined media during most of this work ensured wellcontrolled and simplified experimental conditions, since, unlike natural
media, denned media do not contain any hormones which may complicate the interpretation of results.
Hardy (1950), using natural medium, obtained a differentiation of
mammary ducts from the epidermis of the abdominal skin of mouse
embryos as tubular invaginations of the germinal layer. These tubes
were empty and lined with one layer of cuboidal cells. Lasfargues and
Murray (1959) studied the effect of various hormones, applied singly
or in combination, on growth and differentiation of epithelium and
stroma of the mammary gland from 10-15-day mouse embryos. They
found that in defined medium alone the abdominal epithelium penetrated into the adjacent connective and adipose tissue where it formed
tubes. Addition of either oestradiol or progesterone to the medium
prevented this process; the germinal layer in such cultures became
dissociated and the connective tissue necrotic. A combination of oestradiol with progesterone in the classic proportion of 1 : 1000, however,
did not prevent the differentiation of the mammary ducts normally
seen in control medium but the lining cells were lower or atrophic;
the connective tissue was poor but the adipose tissue was well developed
and showed lipid droplets in the cytoplasm. In contrast, the pituitary
hormones, mammotrophin and somatotrophin, applied singly or
combined greatly stimulated the development of the ducts and also
increased the size of the cells lining the ducts and their number to
3-4 rows. This growth-promoting effect was not diminished if oestradiol
and progesterone or oestradiol alone were included in the combination.
In all three groups the mammary ducts grew well and the epithelium
became hyperplastic, but the quality of the stroma depended on whether
somatotrophin or mammotrophin was present in the mixture. With
somatotrophin the connective tissue of the explants became rich in
ILSE L A S N I T Z K I
(1956) suggested that their effectiveness also depended on the presence
of pituitary hormones, as in hypophysectomized animals steroids only
produced enlargement of the ducts without lobular differentiation.
Lyons, Li and Johnson (1958) postulated a mechanism of mammarygland development in which the pituitary hormones exert an indirect
influence by controlling the function of most endocrine glands including that of the ovary and the adrenal.
Tissue culture experiments, in which the influence of various hormones on the development of the mouse mammary gland grown as
organ culture was investigated, demonstrated a direct effect of the
hormones on the tissue and showed that a combination of hormones
was necessary to achieve growth and differentiation of the immature
organ, and to maintain the structure and function of the adult gland.
The use of defined media during most of this work ensured wellcontrolled and simplified experimental conditions, since, unlike natural
media, denned media do not contain any hormones which may complicate the interpretation of results.
Hardy (1950), using natural medium, obtained a differentiation of
mammary ducts from the epidermis of the abdominal skin of mouse
embryos as tubular invaginations of the germinal layer. These tubes
were empty and lined with one layer of cuboidal cells. Lasfargues and
Murray (1959) studied the effect of various hormones, applied singly
or in combination, on growth and differentiation of epithelium and
stroma of the mammary gland from 10-15-day mouse embryos. They
found that in defined medium alone the abdominal epithelium penetrated into the adjacent connective and adipose tissue where it formed
tubes. Addition of either oestradiol or progesterone to the medium
prevented this process; the germinal layer in such cultures became
dissociated and the connective tissue necrotic. A combination of oestradiol with progesterone in the classic proportion of 1 : 1000, however,
did not prevent the differentiation of the mammary ducts normally
seen in control medium but the lining cells were lower or atrophic;
the connective tissue was poor but the adipose tissue was well developed
and showed lipid droplets in the cytoplasm. In contrast, the pituitary
hormones, mammotrophin and somatotrophin, applied singly or
combined greatly stimulated the development of the ducts and also
increased the size of the cells lining the ducts and their number to
3-4 rows. This growth-promoting effect was not diminished if oestradiol
and progesterone or oestradiol alone were included in the combination.
In all three groups the mammary ducts grew well and the epithelium
became hyperplastic, but the quality of the stroma depended on whether
somatotrophin or mammotrophin was present in the mixture. With
somatotrophin the connective tissue of the explants became rich in