| Summary: | The time of first appearance and distribution of
several types of peptide-sto*. ing cells were studied
in the gastrointestinal tract of chick embryos
between 12 days of incubation ana hatching. Immunocytochemical
methods have been employed to demonstrate
cells immunoreactive for gastrin/cholecystokinin
(CCK), neurotensin, somatostatin, glucagon and
avian pancreatic polypeptide (APP) in the p.oventriculus,
gizzard, pyloric region, duodenum, upper and
lower ileum, caecum and rectum.
No immunoreactive cells were found in any region
at 11 days of incubation. Immunoreactive cells
which first appeared at 12 days were: somatostatinand
neurotensin-immunoreactivc cells in the
y
proventr Lculus, pyloric vs ion and duolenum,
neurotensin-immunoreactive cells in the rectum? at 13
days, APP-immunoreact ive cells in the duodenum and
aiy->r ileuM, glucagon-immunoreact ive cells in the
proventriculus: at 14 d a y s , somatostatin- and
neurotensin-immunoreact ive cells in the upper and
lower ileum, gastrin/CCK-immunoreactive cells in the
small intestine, APP-immunoreact ive cells in the
proventriculus and lower ileum, glucagon-irmunor eacc
ive cells in the pyloric region and small intastine:
at 16 days, gastrin/CCK-immunoreactive cells in the
pyloric region.
Subjective assessment showed an increase in frequency
of all five cell types until the numbers at hatching
were approximated, a few days before hatching. No
immunoreactive cells of any type were detected in the
gizzard; only neurotensin-immunoreact ive cells were
detected in the caecum and rectum.
When these endocrine cells first appeared, the
surface epithelium of the gastrointestinal tract was
relatively undifferentiated. Cells of all five types
were found in glands once morphogenesis h d begun.
The coexistence of APP- and glucagon-1 ike immunoreaetivity
in the same cells was studied in the proventriculus
and small intestine, and of g a s t r m / C C K - and
neurotens in-like immunoreact ivity in the pyloric
region and duodenum. Consecutive sections of each
region were examined at 17$-, 19- and 7 1-days of
incubation. For practical reasons, earlier stages,
when cell numbers were small, were not studied.
However, the trend shown in the proventriculus and
ileum suggests that most, if not all, the relevant
cells may contain APP- and glucagon-like peptides
from the time they first appear. No dual immunoreactivity
was detected in the duodenum. The proportion
of cells demonstrating dual immunoreactivity for
gastrin/CCK and neurotensin showed no clear change in
either region.
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