614
ILSE L A S N I T Z K I
in some explants mono- and multinucleate myoblasts differentiated
from the mesenchyme surrounding the rudiments. Cross-striation,
consisting of A bands and Z discs, appeared in the muscle cells of
explants kept with cortisone but was absent in control explants.
F. I N T E R A C T I O N OF H Y D R O C O R T I S O N E W I T H V I T A M I N A
1. On Epidermis
Fell (1962) investigated the interaction of hydrocortisone and vitamin
A on embryonic chick skin. The vitamin (Roche) inhibits the normal
keratinization of the epidermis and induces a metaplasia, with the
formation of mucus-secreting columnar cells. The feather germs become,
unusually flabby in vitamin A treated explants. In cultures grown for
2 days with a combination of vitamin A and hydrocortisone the feather
germs dilate and form balloon-like cysts and the periderm secretes a
hard viscous substance. Autoradiographic studies (Fell and Pelc,
unpublished work) showed that, like mucus, this substance contained
sulphate, but like keratin it also contained cystine. This secretory
period lasted only for a few days. At 6 days' growth some areas of the
explant began to keratinize, while other regions of the same culture
formed mucus-secreting columnar epithelium. Eventually the typical
effect of vitamin A predominated; the keratin which had formed
under the influence of the hydrocortisone was sloughed and replaced
by mucous epithelium.
2. On Bone
Fell and Thomas (1961) showed that hydrocortisone also reduced
the action of vitamin A on chick and mouse limb-bone rudiments
in vitro. The vitamin causes a severe reduction and an absorption of
the cartilage, with loss of metachromasia, resulting in a severe shrinkage
and distortion of the rudiment. The effect is most marked in the region
where the cells of the proliferative zone become transformed into
hypertrophic chondroblasts: this region then collapses and becomes
detached from the shaft. Simultaneous administration of hydrocortisone
with the vitamin prevented the collapse of this sensitive region; the
growth rate of the bones treated with both compounds began to rise
after the sixth day as compared with those grown with the vitamin
alone, and histological sections gave an almost normal picture. Exposure to hydrocortisone of explants previously treated with vitamin A
failed to arrest the effect of the vitamin A, with the exception of mouse
tibia, which showed a partial recovery. In cultures grown with both
compounds, and transferred to either normal medium or medium
ILSE L A S N I T Z K I
in some explants mono- and multinucleate myoblasts differentiated
from the mesenchyme surrounding the rudiments. Cross-striation,
consisting of A bands and Z discs, appeared in the muscle cells of
explants kept with cortisone but was absent in control explants.
F. I N T E R A C T I O N OF H Y D R O C O R T I S O N E W I T H V I T A M I N A
1. On Epidermis
Fell (1962) investigated the interaction of hydrocortisone and vitamin
A on embryonic chick skin. The vitamin (Roche) inhibits the normal
keratinization of the epidermis and induces a metaplasia, with the
formation of mucus-secreting columnar cells. The feather germs become,
unusually flabby in vitamin A treated explants. In cultures grown for
2 days with a combination of vitamin A and hydrocortisone the feather
germs dilate and form balloon-like cysts and the periderm secretes a
hard viscous substance. Autoradiographic studies (Fell and Pelc,
unpublished work) showed that, like mucus, this substance contained
sulphate, but like keratin it also contained cystine. This secretory
period lasted only for a few days. At 6 days' growth some areas of the
explant began to keratinize, while other regions of the same culture
formed mucus-secreting columnar epithelium. Eventually the typical
effect of vitamin A predominated; the keratin which had formed
under the influence of the hydrocortisone was sloughed and replaced
by mucous epithelium.
2. On Bone
Fell and Thomas (1961) showed that hydrocortisone also reduced
the action of vitamin A on chick and mouse limb-bone rudiments
in vitro. The vitamin causes a severe reduction and an absorption of
the cartilage, with loss of metachromasia, resulting in a severe shrinkage
and distortion of the rudiment. The effect is most marked in the region
where the cells of the proliferative zone become transformed into
hypertrophic chondroblasts: this region then collapses and becomes
detached from the shaft. Simultaneous administration of hydrocortisone
with the vitamin prevented the collapse of this sensitive region; the
growth rate of the bones treated with both compounds began to rise
after the sixth day as compared with those grown with the vitamin
alone, and histological sections gave an almost normal picture. Exposure to hydrocortisone of explants previously treated with vitamin A
failed to arrest the effect of the vitamin A, with the exception of mouse
tibia, which showed a partial recovery. In cultures grown with both
compounds, and transferred to either normal medium or medium