Duodenal Lobe Research Articles

Topographic Differences in Cell Populations and Insulin Secretion in the Endocrine Pancreas of the ToadBufo arenarum

We analyzed the endocrine cell topography within the amphibian pancreas and the relationship of this distribution to lobular variation in insulin content and secretion. Pancreases from adult male toadBufo arenarumwere separated into their five lobes: free, gastric, hepatic, duodenal, and jejunal. Pieces of each lobe were incubated with glucose, arginine, and K+and the insulin concentration in the medium was measured by radioimmunoassay. In the presence of 2 or 8 mMglucose, 10 mMarginine, and 10 mMK+the free lobe released a significantly greater amount of insulin than the other lobes, while the output of the gastric lobe was greater than that of the duodenal, hepatic, and jejunal. At 8 mMglucose, every pancreatic lobe released a significantly higher amount of insulin than at 2 mM. The insulin content of the free lobe was significantly higher than that of the others, whereas this parameter was comparable among the latter. These pancreases contained islets of variable size and irregular shape. B and non-B cells, detected by immunoperoxidase staining, were located at the central and peripheral zones of the islets, respectively. A large number of non-B cells were also scattered over the exocrine component. Morphometrical analyses revealed the following sequence of endocrine cell percentage: free lobe > gastric lobe = duodenal lobe > jejunal lobe = hepatic lobe. Some 48% of the endocrine cells were present in the islets, while the remaining 52% were found throughout the exocrine pancreas. In the free lobe, more endocrine cells were located within the islets (65%) than outside and in the gastric lobe the proportion was almost equal (48% within, 52% outside), but in the hepatic, duodenal, and jejunal lobes the majority lay outside the islets (61, 63, and 70% extrainsular, respectively). The area covered by B and D cells was far larger within the islets than outside, with the relative magnitude of this difference being free lobe > gastric lobe > duodenal lobe > hepatic lobe = jejunal lobe. In the free lobe, this relative distribution was more skewed than in the remaining lobes. PP and A cells occupied a more extensive area outside the islets than inside in every lobe. There were no significant differences among the extrainsular areas occupied by each type of endocrine cell within a given pancreatic lobe. These results constitute the first demonstration of the heterogeneity in morphology, insulin content, and secretory function among the pancreatic lobes inB. arenarum.The data further suggest that the nonuniform secretory capacities of amphibian pancreatic lobes reflect localized differences in their insulin content, which heterogeneity in turn stems from the dissimilar distribution and organization of their constituent endocrine-cell populations.

Peptide YY in the mammalian pancreas: immunocytochemical localization and immunochemical characterization

Peptide YY (PYY) was demonstrated by immunochemical and/or immunocytochemical methods in endocrine cells in the pancreas of adult mice, rats, guinea-pigs, cats, dogs, pigs and cows. In the pancreas of mouse and rat, immunoreactive PYY was observed in a major subpopulation of the glucagon cells (splenic lobe of the pancreas); immunoreactive PYY also occurred in a subpopulation of the pancreatic polypeptide (PP) cells (duodenal lobe), and in a few extra-insular endocrine cells dispersed throughout the pancreatic parenchyma. In the pancreas of cat, dog and pig immunoreactive PYY was found to coexist with PP, but not with glucagon. Radioimmunoassay (RIA) revealed PYY-like material in extracts of pancreas (and colon) of all the species examined. The highest concentrations were found in the pancreas of cat and mouse; moderate amounts were found in the rat and only small amounts were detected in guinea-pig and pig. The concentrations in the pancreas were uniformly much lower than those in the colon. Analysis by high performance liquid chromatography (HPLC) showed that the PYY-immunoreactive material from pancreas (and rat colon) had an elution profile very similar to that of synthetic PYY, and distinct from that of PP and neuropeptide Y.

An immunocytochemical study of the endocrine pancreas in three genera of lacertids

The comparative morphology of the endocrine pancreas was studied in 11 species of lacertids. Four major cell types were identified immunocytochemically in the endocrine pancreas: glucagon-immunoreactive A-cells, insulin-immunoreactive B-cells, somatostatin-(SRIF)-immunoreactive D-cells, and pancreatic polypeptide(PP)-immunoreactive F-cells. Different distributions of the four cell types were seen in the endocrine tissue within the exocrine parenchyma. F-cells were rare or absent in the splenic lobe and abundant in the duodenal lobe, in which they were usually widespread in the exocrine parenchyma and rarer in the islets. The other three cell types were always present in the islets. The central core consisted of B- and A-cells, with B-cells predominating. The peripheral mantle was formed by A-cells and less abundant D-cells. Rare D-cells were also found in the central core. D- and F-cells showed projections often closely associated with capillaries. The observed arrangements in islets and isolated cells may represent an endocrine network that, in addition to systemic actions, may regulate exocrine function in a paracrine fashion.

Morphology and distribution of efferent vagal innervation of rat pancreas as revealed with anterograde transport of Dil

Vagal efferent innervation of the pancreas was labeled by anterograde transport of Dil injected into the dorsal motor nucleus (dmnX). While over the entire organ only 19 ± 3 (or8 ± 1%)of the231 ± 17 interlobular ganglia received Dil-labeled vagal fibers and terminals, the proximal duodenal lobe (or head) was significantly more densely innervated. Laser scanning confocal microscopy revealed further morphological details of the vagal terminals and their target ganglion cells. No vagal fibers or terminals were found in islets and acinar tissue.

Vagal afferent fibers almost exclusively innervate islets in the rat pancreas as demonstrated by anterograde tracing

Anterograde tracing from the nodose ganglion with wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) was utilized to investigate vagal afferent innervation of the rat pancreas. Labelled afferent fibers were consistently detected in islets in all animals. Only about 10% of islets were labelled even in best cases. In only 5 out of 16 rats, acini and excretory ducts received afferent innervation. Injections into the right nodose ganglion resulted in labelling preferentially within the splenic lobe, whereas injections into the left ganglion labelled fibers predominantly in the duodenal lobe. These results point to a non-random distribution of vagal afferent fibers within the pancreas, and suggest a role for these afferents in the regulation of endocrine pancreatic function.

The nude mouse as a model for the study of human pancreatic cancer

The purpose of this study was to characterize an in vivo model of human pancreatic cancer suitable for chemotherapy and immunotherapy studies. In this study we report a 2-year experience in growing the MIA PaCa-2 (CRL 1420) human pancreatic cancer cell line in 92 adult (8 weeks old) and 256 young (3–6 weeks old) nude mice. Ten million tumor cells were transplanted into orthotopic (duodenal lobe of the pancreas) and/or heterotopic positions (hepatic and subcutaneous) and data on operative mortality, effect of total body irradiation (TBI), tumor growth kinetics, and survival are presented comparing the two age groups. Operative mortality was due to anesthetic intolerance which was higher in the young mouse population (13.4% versus 5.7%). Adult mice withstood TBI (500 rad) without mortality but young mice were highly sensitive to radiation damage and their maximum tolerated dose (LD 50) was 425–450 rad. Subcutaneous tumors grew significantly more often in young compared to adult animals (97.9% versus 69%) and this finding was not affected by TBI (96.9% versus 75%), though tumors did appear more quickly after TBI. An average of 14.7 ± 2.8 days was required for the subcutaneous tumors to become macroscopically apparent in the adult population compared with 3.1 ± 0.8 days in the young mice. The largest subcutaneous tumor diameter 28 days following tumor implant averaged 9.3 ± 0.6 mm in the young animals and 5.5 ± 1.7 mm in the adult population ( P < 0.01). Treatment of young mice with human recombinant interleukin-2 (IL-2) (10,000 Units twice a day for 28 days) produced a 27% decrease in tumor growth. This effect was abolished by prior irradiation of the young mice with 375 rad TBI. Pancreatic tumor growth also occurred more consistently in young than in adult animals (91.2% versus 64.3%) and irradiation did not affect pancreatic tumor take in either group. Occasionally intrapancreatic tumor growth was associated with liver metastases in animals that were killed after 28 days (17.8% in young and 22.2% in adult animals). However, when more than 45 days elapsed before sacrificing the animals, the incidence of hepatic metastases increased to 57.1%. This was slightly less than the incidence of hepatic lesions found after direct injection of cancer cells into the liver by portal vein injection (71.4%). Direct extension of tumor into surrounding tissues was common with frequent involvement of the duodenum (83.7%), kidneys (30.6%), and other intraabdominal organs (43.9%). Survival was significantly longer in adult compared to young mice. All young mice that grew intrapancreatic tumors died within 3 months from the injection of tumor cells, while about 50% of the adult animals with documented pancreatic tumors survived up to 5 months. The model is an efficient means for the in vivo study of human pancreatic cancer and the autologous anti-tumor response can be controlled by the use of young and irradiated nude mice by methods described in this paper.

Immunocytochemical component of endocrine cells in pancreatic islets of horses.

The endocrine cell components in the pancreatic islets of the following 4 pancreatic regions of the horse were investigated by immunohistochemical methods: lobus pancreatis sinister (left lobe); lobus pancreatis dexter (right lobe); and 2 regions of Corpus pancreatis (body), the duodenal lobe which lies along the cranial duodenal flexure and descending duodenum, and the intermediate lobe which is situated around the portal vein. The islets in the left and intermediate lobes contained a central mass of glucagon cells surrounded by insulin cells, a few somatostatin cells and sporadic pancreatic polypeptide (PP) cells. On the other hand, the islets in the duodenal lobe were small in size compared with the other 3 regions, and were predominant in insulin and pancreatic polypeptide (PP) cells, but almost lacked in glucagon cells. These findings suggested that the duodenal lobe was derived from the ventral pancreatic primordium, and the left and intermediate lobes were originated from the dorsal pancreatic primordium. In the right lobe, the composition and distribution of the islet cells were almost the same as those in the left and intermediate lobes, but there were several lobules containing numerous PP cells as seen in the duodenal lobe.

Nonadrenergic sympathetic neural influences on basal pancreatic hormone secretion.

Evidence for peptidergic innervation of the islets of Langerhans is increasing, yet the role of neuropeptides in mediating neurally induced changes of islet function is not clear. To determine if nonadrenergic transmitters make an important contribution to sympathetic neural effects on basal pancreatic hormone secretion, we examined the effect of local sympathetic nerve stimulation (SNS) on the output of immunoreactive insulin (IRI), immunoreactive glucagon (IRG), and somatostatin (SLI) from the duodenal lobe of the pancreas in situ in halothane-anesthetized dogs, under conditions where the actions of the classical transmitter norepinephrine (NE) should be blocked by propranolol (PROP) and yohimbine (YO). In the absence of adrenergic antagonists, SNS rapidly reduced the output of IRI (delta = -1.34 +/- 0.91 mU/min) and SLI (delta = -600 +/- 350 fmol/min) and stimulated that of IRG (delta = +1.39 +/- 0.57 ng/min). In the presence of PROP and YO, SNS induced similar changes of hormone secretion: delta IRI, -1.30 +/- 0.53 mU/min; delta SLI, -480 +/- 180 fmol/min; delta IRG = +1.89 +/- 0.63 ng/min. Because PROP and YO abolished the pancreatic effects of high dose infusions of NE (1 microgram.kg-1.min-1 iv), we suggest that the antagonists produced sufficient, combined adrenergic blockade at the level of the islet, and we conclude that a nonadrenergic neurotransmitter or modulator plays a major role in mediating sympathetic neural effects on basal islet hormone secretion.

The presence and actions of NPY in the canine endocrine pancreas

Immunofluorescent staining for neuropeptide Y (NPY) in canine pancreatic tissue was performed together with an evaluation of the effects of synthetic NPY on the release of insulin (IRI), glucagon (IRG) and somatostatin (SLI) from the duodenal lobe of the canine pancreas in situ. NPY-like immunoreactivity was localized in perivascular nerve fibers throughout the acinar tissue. NPY-immunoreactive fibers were also demonstrated in the islets, usually surrounding blood vessels but also occasionally in fibers associated with endocrine cells, primarily at the periphery of islets. In addition, the ganglia dispersed in the pancreatic parenchyma were densely innervated by NPY-immunoreactive fibers, and these ganglia regularly contained cell bodies staining for NPY. Direct infusion of NPY into the pancreatic artery (p.a.) produced a dose-dependent decrease of pancreatic SLI output and of pancreatic venous blood flow. Low-dose p.a. infusion of NPY (50 pmol/min) had no effect on basal IRI or IRG output or on the islet response to glucose (5-g bolus, i.v.). High-dose p.a. infusion of NPY (500 pmol/min) transiently stimulated IRI output and modestly increased IRG output. However, the comparatively sparse innervation of canine islets with NPY-like immunoreactive fibers and the relatively minor effects of large doses of synthetic NPY on pancreatic hormone release lead us to conclude that this peptide is not an important neuromodulator of islet function in the dog.

Organ explant culture of adult Syrian golden hamster pancreas.

An organ explant culture system has been developed for long term maintenance of adult pancreatic tissue from the Syrian golden hamster. Gastric and duodenal lobe explants of up to 0.5 cm2 size were placed in tissue culture dishes (60 mm2) on Gelfoam sponge rafts to which was added 5 ml of CMRL medium 1066 supplemented with heat inactivated newborn bovine serum, L-glutamine, hydrocortisone, insulin, and antibiotics. Dishes were placed in a controlled atmosphere chamber, which was gassed with 45% O2, 50% N2, and 5% CO2 and incubated at 36.5 degrees C. Viability of the tissues was determined by light and electron microscopy as well as by [3]thymidine incorporation. Explants were viable for up to 70 d. Zymogen granule-containing cells characteristic of acinar cells and mucus-containing cells characteristic of ductal cells were present throughout this period. However, endocrine cells were only present for the 1st wk in culture.

Regional distribution of pancreatic polypeptide-like immunoreactivity in the canine brain

Recently many gut hormones have been found in the brain, and there is some evidence to suggest that pancreatic polypeptide-like immunoreactivity (PP-LI) is also present in the brain. Although in mammals, confirmative evidence is not yet shown. In the present paper we report the distribution and tissue localization of PP-LI in the canine brain by radio-immunoassay (RIA) and immunohistochemistry. Normal, fasted mongrel dogs were used. Brain tissue was extracted by boiling water. High concentrations of PP-LI were found in the pituitary gland (3.67 +/- 1.10 ng/g wet wt), substantia nigra (1.58 +/- 0.36 ng/g wet wt), hypothalamus (0.74 +/- 0.28 ng/g wet wt) and olfactory lobe (0.58 +/- 0.21 ng/g wet wt). PP-LI was not detectable in the frontal lobe, parietal lobe, striatum, thalamus, hippocampus, pons, cerebellum and medulla oblongata. The amounts of PP-LI in the brain were more less than the amounts of PP present in the pancreas (duodenal lobe, 29.3 +/- 1.1 microgram/g wet wt). The dilution curve of the brain tissue extracts showed parallelism with the standard curve of human and porcine PP on the RIA system. On Bio-Gel P-30 column chromatography, PP-LI from the pituitary gland and olfactory lobe eluted as a single peak coincided with highly purified bovine PP. In immunohistochemical study, PP-LI was found in the intermediate lobe and the stalk of the pituitary gland by means of anti-bovine PP antiserum. These findings of the specific regional localization suggest that PP or PP-LI may have a physiological role in the central nervous system.

Pancreatic polypeptide (PP) cells in the PP-rich lobe of the human pancreas are identified ultrastructurally and immunocytochemically as F cells.

The ultrastructure of immunohistochemically identified PP cells has been investigated by applying the serial semithin/thin section technique to the human pancreas, with special reference to the posterior part of the head, reputed to originate from the ventral primordium. PP cells of this area differ from those already identified in the rest of the pancreas and correspond to a cell, not yet described in the human pancreas, characterized by larger granules of very variable shape and structure. Such granules resemble those of so-called "F cells", i.e. the PP cells of dog uncinate process and cat duodenal lobe, also coming from the ventral primordium. Thus, human "ventral lobe" PP cells have peculiar potentialities which are expressed in distinctive structural patterns of presently unknown functional meaning.

Elevated levels of pancreatic polypeptide in obese-hyperglycemic mice

The concentration and distribution of pancreatic polypeptide (PP) was studied in hyperglycemic obese (ob/ob) mice and homozygous (+/+) controls. By radioimmunoassay, the concentration of PP in the pancreas of ob/ob mice was greater both in the duodenal lobe (70.7%) and in the body and tail (66.3%) when compared to identical areas of control pancreases. Analysis of immunostained pancreatic tissue indicated that the number of PP cells per islet cross-section was significantly increased (58%) in the ob/ob tissue. The calculated total number of PP cells per average islet was elevated three times in the ob/ob islet. However, the proportion PP cell volume relative to the islet volume in ob/ob was one-half that of control islets. These results clearly demonstrate an elevation in both the number of PP cells per islet and the concentration of PP in the diabetic ob/ob murine pancreas.