16. A C T I O N S OF H O R M O N E S
609
during the first 24 h. Thus a concentration of 0-1 /xg had a very slight
effect, but 10/xg killed 45°/o of lymphocytes within 2 days. Purine and
pyrimidine bases added simultaneously with cortisone slightly diminished the cytotoxic action, while potassium, insulin and testosterone
had no influence. Lymph nodes cultured for 3 | h with cortisone (3-3
/xg/ml) and transferred to normal medium for the remainder of the
48 h culture period showed only a very slight increase of pycnosis over
that of the normal. This indicates that cortisone does not cause immediate and irreversible damage but that the length of exposure is
important (see also Vol. 2, Chapter 2).
B. EFFECTS ON D I F F E R E N T I A T I O N OF M E L A N O P H O R E S
Hamilton (1941) has shown that deoxycorticosterone directly
inhibits the formation of melanophores in embryonic skin grown in vitro.
Skin explants from New Hampshire Red and Barred Rock chick
embryos contain colourless melanoblasts if derived from young embryos.
These develop in culture into coloured melanophores. Epidermis from
older embryos show a great number of fully differentiated black and
a small number of red melanophores. In the young explants, the
hormone arrests the differentiation of the melanoblasts, and these
remain colourless. In the older skin grown with deoxycorticosterone
the existing differentiated melanophores contract, round up, degenerate
and are not replaced by new ones. This effect differs from that of the
sex hormones, which affect only the rate of melanin synthesis but not
the number of melanophores, while deoxycorticosterone inhibits the
formation of new melanoblasts and also their differentiation.
C. EFFECTS ON T H E S E C R E T O R Y A C T I V I T Y OF T H E K I D N E Y
The adrenal cortex plays an important part in the maintenance of
renal function. In adrenalectomized dogs the renal tubules failed to
maintain the concentration difference of certain ions between plasma
and urine (Harrison and Darrow, 1939). Chambers and Cameron
(1944) demonstrated a direct influence of corticosteroids on the secretory activity of chick kidneys grown in vitro. Kidneys from 9-day
chick embryos form closed tubular segments in vitro by proliferation
at the cut ends. These tubes become gradually distended with secreted
fluid. The authors compared the effect of Kendall's compound A
(11-dehydrocorticosterone) with that of compound E (17-hydroxy-l 1dehydrocorticosterone) and the whole of Kendall's extract on the
secretory action of these tubules. The hormones were administered
either by immersion of 48 h cultures, or by the addition of the compounds to the medium of 48 h cultures, or to that of fresh explants.
x
609
during the first 24 h. Thus a concentration of 0-1 /xg had a very slight
effect, but 10/xg killed 45°/o of lymphocytes within 2 days. Purine and
pyrimidine bases added simultaneously with cortisone slightly diminished the cytotoxic action, while potassium, insulin and testosterone
had no influence. Lymph nodes cultured for 3 | h with cortisone (3-3
/xg/ml) and transferred to normal medium for the remainder of the
48 h culture period showed only a very slight increase of pycnosis over
that of the normal. This indicates that cortisone does not cause immediate and irreversible damage but that the length of exposure is
important (see also Vol. 2, Chapter 2).
B. EFFECTS ON D I F F E R E N T I A T I O N OF M E L A N O P H O R E S
Hamilton (1941) has shown that deoxycorticosterone directly
inhibits the formation of melanophores in embryonic skin grown in vitro.
Skin explants from New Hampshire Red and Barred Rock chick
embryos contain colourless melanoblasts if derived from young embryos.
These develop in culture into coloured melanophores. Epidermis from
older embryos show a great number of fully differentiated black and
a small number of red melanophores. In the young explants, the
hormone arrests the differentiation of the melanoblasts, and these
remain colourless. In the older skin grown with deoxycorticosterone
the existing differentiated melanophores contract, round up, degenerate
and are not replaced by new ones. This effect differs from that of the
sex hormones, which affect only the rate of melanin synthesis but not
the number of melanophores, while deoxycorticosterone inhibits the
formation of new melanoblasts and also their differentiation.
C. EFFECTS ON T H E S E C R E T O R Y A C T I V I T Y OF T H E K I D N E Y
The adrenal cortex plays an important part in the maintenance of
renal function. In adrenalectomized dogs the renal tubules failed to
maintain the concentration difference of certain ions between plasma
and urine (Harrison and Darrow, 1939). Chambers and Cameron
(1944) demonstrated a direct influence of corticosteroids on the secretory activity of chick kidneys grown in vitro. Kidneys from 9-day
chick embryos form closed tubular segments in vitro by proliferation
at the cut ends. These tubes become gradually distended with secreted
fluid. The authors compared the effect of Kendall's compound A
(11-dehydrocorticosterone) with that of compound E (17-hydroxy-l 1dehydrocorticosterone) and the whole of Kendall's extract on the
secretory action of these tubules. The hormones were administered
either by immersion of 48 h cultures, or by the addition of the compounds to the medium of 48 h cultures, or to that of fresh explants.
x