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of the ducts (i.e., the wider the lumen, the higher
the epithelium). The common duct is lined with a
single row (or two) of columnar cells occasionally
with interspersed goblet cells, which are absent in
two-week-old hamsters but occur with moderate
frequency in the entire common duct of adult
animals and become a prominent constituent of
the epithelium after one year 95 . According to
McMinn and Kugler 108 , the luminal surface and
supra-nuclear regions of the common duct cells
contain glycogen and lack alkaline phosphatase
but give a strongly positive reaction for succinic
dehydrogenase. This suggests an active
engagement of cells in transport mechanisms.
The common duct has the largest lumen, thickest
periductal connective tissue, and largest epithelial
cells of any other pancreatic duct. Because of its
anatomical and topographical patterns, step
sections of the histological material are necessary
to demonstrate the entire length of the common
duct. A few small pancreatic ducts (peri-biliary
ducts) enter the common bile duct directly. The
common bile duct merges imperceptibly into the
epithelium of the duodenum. After piercing the
muscular wall of the duodenum, and while
transversing the intestinal mucous membrane
(Fig. 18), the duct lining is drawn into folds, but no
diverticula comparable to those in the mouse
were seen 108 . A specific sphincter, as in humans,
is lacking in the hamster.
18
Rosenberg et al. examined of the effects of aging
on the uptake of tritiated thymidine (3H-TdR) by
the different cell types of the pancreas of the
SGH. Eight to 22-week-old animals received 3H-
TdR (2 microCi/gm) intra-peritoneally and were
sacrificed one h later. Pancreatic tissue from each
animal was processed for autoradiography. The
percentage of acinar cells labeled with 3H-TdR
was 1.17 ± 0.26 at eight-weeks-old and steadily
diminished to 0.02 ± 0.00 at 22 weeks. The
percentage of ductular and islet cells labeled with
3H-TdR at eight weeks was 0.24 ± 0.24 and 0.16
± 0.01, respectively. At 22 weeks it was 0.13 ±
0.09 and 0.18 ± 0.01, respectively. In contrast
with acinar cells, the percentage of ductular and
islet cells labeled with 3H-TdR between 10 and 20
weeks-old showed considerable variability. In the
main ducts, the number of epithelial cells per mm
duct length labeled with 3H-TdR did not change
throughout the study (3.25 ± 1.5 at eight weeks
and 3.35 ± 1.3 at 22 weeks). It was concluded
that acinar cell growth is an inverse function of
age between eight and 22 weeks and that
differentiated cell types in the pancreas of the
SGH are capable of incorporating 3H-TdR during
the S-phase of the cell cycle 109 .
By scanning electron microscopic examination no
clearly defined border between centroacinar cells
and the beginning of ductules could be
distinguished in the numerous SEM pancreatic
Figure 18. Common duct piercing through the duodenal wall to open into the duodenum. H&E, X 12.