16.
A C T I O N S O F H O R M O N E S
597
tures immersed for short periods in Tyrode's solution containing insulin
and subsequently grown in normal medium showed a stimulation of
glycogen synthesis similar to that seen in explants exposed continuously to the hormone. The effects of insulin in vitro were identical
with those observed in vivo in the brown adipose tissue of the rat after
denervation (Sidman and Fawcett, 1954). This suggests that denervation may increase the sensitivity of adipose tissue to circulating
insulin.
B . E F F E C T S O N F O E T A L B O N E
It has been shown that insulin causes a severe micromelia of chick
embryos in ovo (Landauer, 1947a, b ; Duraiswami, 1950) and it is
interesting to speculate whether this is due to hypoglycaemia or to a
direct effect of the hormone on the bones.
Chen (1954) investigated this problem in organ cultures of chickembryo bone rudiments grown in the presence of insulin. Femora,
tibiae, humeri, radii and ulnae of 6|-day chick embryos were cultivated
for 10 days in natural medium containing embryo extract to which
0-16-0*0016 i.u. insulin had been added.
Early bone rudiments explanted in control medium grow and
develop in a fairly normal way and increase to three to four times
their original length within 7-10 days (Fell and Robison, 1929;
Fell, 1951). They differentiate into three regions: the hypertrophic
cartilage in the shaft, consisting of chondroblasts in well-defined
capsules, and separated by thick partitions of matrix, followed distally by an area of proliferative flat cells and smaller epiphyseal cells.
The layer of periosteal tissue around the middle of the shaft thickens
during cultivation and extends towards both ends, while a fairly
thick layer of periosteal bone is deposited on the diaphyseal cartilage.
Insulin-treated rudiments grew at a normal rate during the first two
days of cultivation but after this period they elongated more slowly than
their controls. After 5-6 days treatment, the two ends had enlarged
abnormally and the shaft became considerably bent. The thick periosteal layer, which in the controls thinned owing to the lengthening of
the diaphysis, persisted in the treated explants. The surrounding soft
tissue grew much more profusely than that of the control bones.
Histological examination of the treated rudiments after 10 days' culti<
FIG. 1 (above). Brown fat of an 18-day rat cultured for 2 days in serum. The cells contain
little glycogen and only small drops of lipid. PAS haemalum, x 460. (From Sidman, 1956b.)
FIG. 2 (below). Similar culture kept for 2 days in serum containing 4 /ng/ml insulin. The cells
are rich in cytoplasmic glycogen which appears black. Lipid droplets which appear as empty
spaces in this paraffin-embedded tissue are increased in size as compared with the controls.
PAS haemalum. x 460. (From Sidman, 1956b.)
A C T I O N S O F H O R M O N E S
597
tures immersed for short periods in Tyrode's solution containing insulin
and subsequently grown in normal medium showed a stimulation of
glycogen synthesis similar to that seen in explants exposed continuously to the hormone. The effects of insulin in vitro were identical
with those observed in vivo in the brown adipose tissue of the rat after
denervation (Sidman and Fawcett, 1954). This suggests that denervation may increase the sensitivity of adipose tissue to circulating
insulin.
B . E F F E C T S O N F O E T A L B O N E
It has been shown that insulin causes a severe micromelia of chick
embryos in ovo (Landauer, 1947a, b ; Duraiswami, 1950) and it is
interesting to speculate whether this is due to hypoglycaemia or to a
direct effect of the hormone on the bones.
Chen (1954) investigated this problem in organ cultures of chickembryo bone rudiments grown in the presence of insulin. Femora,
tibiae, humeri, radii and ulnae of 6|-day chick embryos were cultivated
for 10 days in natural medium containing embryo extract to which
0-16-0*0016 i.u. insulin had been added.
Early bone rudiments explanted in control medium grow and
develop in a fairly normal way and increase to three to four times
their original length within 7-10 days (Fell and Robison, 1929;
Fell, 1951). They differentiate into three regions: the hypertrophic
cartilage in the shaft, consisting of chondroblasts in well-defined
capsules, and separated by thick partitions of matrix, followed distally by an area of proliferative flat cells and smaller epiphyseal cells.
The layer of periosteal tissue around the middle of the shaft thickens
during cultivation and extends towards both ends, while a fairly
thick layer of periosteal bone is deposited on the diaphyseal cartilage.
Insulin-treated rudiments grew at a normal rate during the first two
days of cultivation but after this period they elongated more slowly than
their controls. After 5-6 days treatment, the two ends had enlarged
abnormally and the shaft became considerably bent. The thick periosteal layer, which in the controls thinned owing to the lengthening of
the diaphysis, persisted in the treated explants. The surrounding soft
tissue grew much more profusely than that of the control bones.
Histological examination of the treated rudiments after 10 days' culti<
FIG. 1 (above). Brown fat of an 18-day rat cultured for 2 days in serum. The cells contain
little glycogen and only small drops of lipid. PAS haemalum, x 460. (From Sidman, 1956b.)
FIG. 2 (below). Similar culture kept for 2 days in serum containing 4 /ng/ml insulin. The cells
are rich in cytoplasmic glycogen which appears black. Lipid droplets which appear as empty
spaces in this paraffin-embedded tissue are increased in size as compared with the controls.
PAS haemalum. x 460. (From Sidman, 1956b.)