The volume and area of the capillaries in the endocrine and exocrine pancreas of the rat

Summary The capillary volumes in the endocrine and exocrine parenchyma of the pancreas were compared with a point-sampling technique. The islets were found to have a capillary volume of approximately 3.5%, while the value for the exocrine pancreas was significantly (P<0.001) lower at 2%. When the capillary wall area was measured, however, both types of parenchyma had a similar value of approximately 20 mm²/mm³ tissue. The reason for the discrepancy between these parameters is probably the lack of lymphatic capillarics, with their relatively small lumen in the islets.     

An immunocytochemical study of the distribution of pancreatic endocrine cells in chicks,with special reference to the relationship between pancreatic polypeptide and somatostatin-immunoreactive cells

Summary Araldite sections of formalin-fixed pancreas from chicks at hatching were treated by an indirect immuno-enzyme technique to reveal cells containing APP, somatostatin, glucagon and insulin.APP cells were found scattered in the exocrine parenchyma. A few were associated with insulin-containing B islets and occasional cells occurred in and around glucagon-containing A islets. Somatostatin-immunoreactive cells were distributed peripherally in A and B islets and were dispersed in the exocrine tissue. APP cells were roughly as numerous in the exocrine parenchyma as somatostatin-immunoreactive cells.Since certain published observations point to the possible occurrence of APP and somatostatin in the same cells, consecutive sections were stained for these hormones. In no case did the two peptides occur in the same cell. Sections subjected to double-staining confirmed this result. Therefore it is likely that the described differences between APP and somatostatin-immunoreactive cells are valid.     

Galanin-immunoreactive nerves in the mouse and rat pancreas

Summary Galanin-containing nerve fibers have previously been observed in the human, dog, and pig pancreas. Whether the mouse and rat pancreas also contain galanin nerve fibers has been a matter of debate. Therefore, we examined the distribution of galanin in the mouse and the rat pancreas. Further, the possible localization of galanin to adrenergic nerves was studied using sequential immunostaining for galanin and tyrosine hydroxylase (TH). In the mouse pancreas, numerous galanin-immunoreactive (GIR) nerve fibers occurred around blood vessels. They were less numerous in the exocrine parenchyma and in association with the islets. In contrast, in the rat pancreas, only a few GIR nerves were found. They were located around blood vessels and scattered in the exocrine parenchyma. Occasionally, GIR nerves were also observed in the islets. There was a dense distribution of TH-immunoreactive fibers in both the mouse and the rat pancreas. Sequential immunostaining revealed co-localization of galanin and TH immunoreactivity in nerve fibers in both the mouse and the rat pancreas. Following chemical sympathectomy using 6-hydroxydopamine (6-OHDA), not all GIR nerves disappeared. In the mouse pancreas a remaining population of galanin nerves was found around blood vessels, and occasionally in the islets. In the rat pancreas, a few GIR nerves were seen also after chemical sympathectomy. We conclude that intrapancreatic GIR nerves also occur in the mouse and the rat. These findings suggest that many of the GIR nerves are adrenergic but that non-adrenergic, possibly intrinsic or sensory GIR nerves exist as well in both the mouse and the rat pancreas.     

An immunocytochemical study of the distribution of pancreatic endocrine cells in chicks, with special reference to the relationship between pancreatic polypeptide and somatostatin-immunoreactive cells.

Araldite sections of formalin-fixed pancreas from chicks at hatching were treated by an indirect immuno-enzyme technique to reveal cells containing APP, somatostatin, glucagon and insulin. APP cells were found scattered in the exocrine parenchyma. A few were associated with insulin-containing B islets and occasional cells occurred in and around glucagon-containing A islets. Somatostatin-immunoreactive cells were distributed peripherally in A and B islets and were dispersed in the exocrine tissue. APP cells were roughly as numerous in the exocrine parenchyma as somatostatin-immunoreactive cells. Since certain published observations point to the possible occurrence of APP and somatostatin in the same cells, consecutive sections were stained for these hormones. In no case did the two peptides occur in the same cell. Sections subjected to double-staining confirmed this result. Therefore it is likely that the described differences between APP and somatostatin-immunoreactive cells are valid.     

Distribution and frequency of endocrine cells in the pancreas of the ddY mouse: an immunohistochemical study

The regional distribution and frequency of pancreatic endocrine cells in ddY mice were studied by an immunohistochemical (peroxidase anti-peroxidase; PAP) method using four types of specific antisera against insulin, glucagon, somatostatin and human pancreatic polypeptide (hPP). In the pancreatic islets, most of insulin-immunoreactive (IR) cells were located in the central portion. Most of glucagon- and somatostatin-IR cells were observed in peripheral regions although a somewhat smaller number of cells were also located in the central regions. HPP-IR cells were randomly distributed throughout the entire islets. In the exocrine pancreas, insulin-, glucagon-, somatostatin- and hPP-IR cells were detected; they occurred mainly among the exocrine parenchyma as solitary cells. Cell clusters consisted of only insulin- or only glucagon-IR cells and were distributed in the pancreas parenchyma as small islets. In addition, insulin- and glucagon-IR cells were also demonstrated in the pancreatic duct regions. Insulin-IR cells were located in the epithelium and sub-epithelial connective tissue regions as solitary cells and/or clusters (3-4 cells), and glucagon-IR cells were mainly located in the epithelium as solitary cells. Overall, there were 63.89+/-5.39% insulin-, 26.52+/-3.55% glucagon-, 7.25+/-2.83% somatostatin- and 1.90+/-0.58% hPP-IR cells. In conclusion, some strain-dependent characteristic distributional patterns of pancreatic endocrine cells were found in the ddY mouse.     

Formation of human islands of Langerhans cells from the epithelium of the acini and ducts]

The contents of endocrine cells in the epithelium of ducts and the number of acino-insular elements in exocrine parenchyma and in pancreatic islets were estimated by means of the dotted method in semithin sections prepared from the pancreas of the human embryos (4--7 months of embryogenesis) and of adult persons (40--50 years of age). Endocrine cell formation was noted in all stages studied in ontogenesis. Quantitative data demonstrated that the epithelium of the ducts is the main source for insulocyte formation. In the pancreas of both human embryos and adult persons, acino-insular transformation participated in the formation of endocrine elements. The data obtained gave a certain evidence on entodermal origin of the pancreatic islets in the human pancreas.     

Modulation of the expression of histocompatibility antigens class I (HLA-A,B,C) in the human pancreas

In this study the expression of HLA class I molecules was analysed on caudal portions of ten pancreata from cadaver donors by means of indirect immunoperoxidase and immunophosphatase techniques. In 7 out of ten pancreata the results showed that islets tissue was almost negative for the expression of HLA Class I antigens as opposed to exocrine tissue that appeared positive. Within exocrine tissue and large sized islets strongly positive interstitial cells were also detected. Double stainings showed that the strongly positive interstitial cells expressed also Leu M1 antigens. Preliminary studies on the remaining three pancreata demonstrate an increase of hematic interstitial cells together with a parallel increase of HLA class I antigens by endocrine parenchyma. The above data suggest that an increase of interstitial cells within pancreas may influence islets antigenicity.     

Pancreatic microcirculation in the common tree shrew (Tupaia glis) as revealed by scanning electron microscopy of vascular corrosion casts.

Pancreatic vascular casts of the common tree shrew (Tupaia glis) were prepared by infusion of Batson's No. 17 plastic mixture into the blood vessels and examined by scanning electron microscopy (SEM). Routine histological study of the pancreas was also performed. It was found that the A and D cells appeared to occupy the core whereas the B cells were found at the periphery of the islets of Langerhans. With SEM, the insular arteriole, a branch of the interlobular artery, was shown to penetrate deeply into the core of the islets before branching off into the glomerular capillary network supplying the islets. These capillaries reunited at the periphery of the islets to become vasa efferentia and then gave off capillaries to anastomose with those in the exocrine part of the pancreas, the insuloacinar portal system. Such an insuloacinar portal system found in the pancreas of the tree shrew was similar to that found in the horse and monkey. However, there were some intralobular arterioles which did not end in the islets but directly branched into the interacinar capillary network and periductular plexus. The capillaries in the exocrine part not only gathered into intralobular venules which confluently formed the interlobular vein but also supplied the duct system. The periductular plexus also collected blood into the intralobular venule and interlobular vein, respectively.     

Ontogeny of rat pancreatic polypeptide (PP) cells

Summary Cells storing pancreatic polypeptide (PP) appear in rat pancreas at the time of parturition, much later than insulin and glucagon cells. At this stage, the pancreatic polypeptide (PP) cells occur scattered in the exocrine parenchyma and in the islets. Subsequently, 5–7 days postnatally, an abrupt increase in the number of PP cells occurs. At this stage, they are fairly numerous in the islets and comparatively rare in the exocrine parenchyma. Not until 8–10 days after birth is the number of PP cells similar to that in the adult pancreas. A few PP cells were seen in the antral mucosa during the first 10 days after birth. They were not seen elsewhere in the gut.     

Dissociation of Langerhans islets in the rabbit after pancreatic duct ligation. Immunocytochemical and ultrastructural studies

In the rabbit, pancreatic duct ligation leads to serious disturbances of the pancreatic endocrine parenchyma. Immunocytochemical studies conducted over a short period (between 5 and 30 days post ligation) allow observation of a progressive dissociation of the Langerhans islets which initially affects the splenic part of the pancreas, a region where numerous large islets are found. This dissociation is followed by a dispersion of small heterologous endocrine cell clusters or isolated endocrine cells in a connective tissue which replace the exocrine parenchyma. On the 30th day after ligation ultrastructural studies show marked degranulation of the B cells demonstrating the great fragility of these cells. These observations of insular dissociation, scattering of the different endocrine cells and impairment of B cells are often reported in experimental and pathological studies of the pancreas.     

Innervation of the pancreas by vasoactive intestinal polypeptide (VIP) immunoreactive nerves

The vasoactive intestinal polypeptide (VIP) has been shown to exert effects on endocrine and exocrine pancreatic secretion. Immunocytochemistry reveals that VIP immunoreactive nerves occur in the porcine, canine, feline and avian pancreas. In the pancreas of pig and cat VIP nerves are abundant around non-immunoreactive nerve cell bodies of the intrapancreatic ganglia but scarce in the islets and in the exocrine parenchyma. In the dog pancreas, however, the intrapancreatic ganglia contain strongly immunoreactive VIP nerve cell bodies which give off axons that seem to heavily innervate vessels as well as endocrine and exocrine cells. We suggest that in the pig and cat the pancreatic VIP nerves mainly affect the activity of a second type of intrapancreatic neuron, whose transmitter is unknown, whereas in the dog pancreas VIP nerves directly contact their putative effector structures.     

An immunohistochemical study of the insulin-, glucagon- and somatostatin-immunoreactive cells in the developing pancreas of the chicken embryo

The distributions and relative frequencies of insulin-, glucagon- and somatostatin-immunoreactive cells were studied in dorsal, ventral, third and splenic lobes of developing chicken pancreas during embryonic periods (10 days of incubation to hatching) by immunohistochemical methods. The regions of pancreas were subdivided into three regions: exocrine, light and dark islet. Round, oval and spherical shaped immunoreactive cells were detected in all four lobes. According to developmental stages, the types of lobes and the regions of pancreas showed various distributions and relative frequencies. In the splenic lobes, insulin, glucagon and somatostatin-immunoreactive cells were detected in exocrine, dark islet and light islet from time differentiation of splenic lobes, 13 days of incubation. The insulin- and somatostatin-immunoreactive cells of the third lobes were detected in exocrine and light islets from 10 days of incubation, and in dark islets from 15 and 11 days of incubation respectively. Glucagon-immunoreactive cells were detected in exocrine, dark and light islets from 16, 11 and 19 days of incubation respectively. These immunoreactive cells of the ventral lobes were detected in exocrine and light islets. However, dark islets were not found in this lobe. Insulin-immunoreactive cells were demonstrated from 10 days of incubation in these two regions. Glucagon-immunoreactive cells were detected from 17 days of incubation in exocrine and 16 days of incubation in the light islets. Somatostatin-immunoreactive cells were demonstrated from 11 days of incubation in exocrine and 14 days of incubation in the light islets. In the dorsal lobes, insulin-immunoreactive cells were demonstrated in exocrine, dark and light islets from 12, 14, and 13 days of incubation, respectively. Glucagon- and somatostatin-immunoreactive cells were detected in dark and light islets from 13 and 14 days of incubation, respectively. Glucagon- and somatostatin-immunoreactive cells were demonstrated from 10 and 11 days of incubation in exocrine respectively. Generally, insulin-immunoreactive cells were increased in light islets but decreased in light islets with developmental stages. However, glucagon-immunoreactive cells were decreased in light islets but increased in dark islets. In addition, somatostatin-immunoreactive cells showed the same frequencies in light and dark islets with developmental stages except exocrine which increased with developmental stages.     

The primary structure of peptide Y (PY) of the spiny dogfish, Squalus acanthias: immunocytochemical localisation and isolation from the pancreas.

1. Endocrine cells within islets, exocrine parenchyma and ductal epithelium in the pancreas of the spiny dogfish, Squalus acanthias, were immunostained with an antiserum to the C-terminal region of mammalian neuropeptide Y (NPY). 2. Radioimmunoassay of pancreatic extracts with the same antiserum detected immunoreactivity in the dorsal lobe (338 pmol/g) and ventral lobe (433 pmol/g). Reverse phase HPLC analysis of both extracts resolved a single immunoreactive peptide. 3. The primary structure of the isolated peptide was established as: YPPKPENPGEDAPPEELAKYYSALRHYINLITRQRY.NH2. 4. Peptide Y (PY) from Squalus acanthias is identical in primary structure to an NPY-related peptide isolated from the pancreas of Scyliorhinus canicula and has a 31/36 residue homology with porcine NPY. The 5 substitutions are highly-conservative.     

The endocrine pancreas of a squamate reptile, the desert lizard (Chalcides ocellatus). A histological and immunocytochemical investigation

The endocrine pancreas of the desert lizard (Chalcides ocellatus) was investigated histologically and immunocytochemically. The endocrine tissue was concentrated in the dorsal lobe, where it constituted about 7% of the total volume. In the ventral lobe the endocrine tissue formed approximately 1% of the total volume. Four endocrine cell types were observed in the pancreas of this species, namely insulin-, glucagon-, somatostatin- and pancreatic polypeptide (PP)-immunoreactive cells. The volume occupied by these cells was 1, 1, 0.6 and 0.3% of the total volume of the pancreas, respectively. Insulin-immunoreactive cells were located in the islet centre and comprised 3% of dorsal and 0.2% of the ventral lobe volume. Glucagon cells occurred at the islet periphery and amounted to 3 and 0.2% of the volume of the dorsal and ventral lobes, respectively. Somatostatin-immunoreactive cells were located at the islet periphery as well as in between the exocrine parenchyma. They constituted 1 and 0.2% of the volume of the dorsal and ventral lobes, respectively. PP-immunoreactive cells occurred mainly among the exocrine parenchyma as solitary cells. They formed only 0.03% of the volume of the dorsal lobe. The corresponding figure in the ventral lobe was 0.6%.     

Rapid isolation of pancreatic islets from collagenase digested pancreas by sedimentation through Percol at unit gravity.

A Percoll solution with a density of 1.045 g/ml was used to separate pancreatic islets and exocrine tissue from collagenase-digested human and $\text{ob/ob}$ mouse pancreases by sedimentation at unit gravity. Most exocrine tissue from the mouse was found to range in density from 1.015 to 1.045 g/ml whereas the denser islets lay in a narrower range of 1.065–1.070 g/ml. Up to 400 islets were obtained from each mouse pancreas and 140 islets from 4 g of human pancreas; the isolated islets being essentially free from contamination with exocrine tissue. Glucose-stimulated insulin release was the same whether the mouse islets were isolated with or without Percoll. The simplicity of the method makes it suitable for large-scale islet isolation, a feature of potential importance for the treatment of diabetes by islet transplantation.     

An immunohistochemical study of the pancreatic endocrine cells of the nude mouse, Balb/c-nu/nu

The regional distribution and frequency of the pancreatic endocrine cells in the nude mouse, Balb/c-nu/nu were studied by immunohistochemical (peroxidase anti-peroxidase; PAP) methods using specific antisera against insulin, glucagon, somatostatin and human pancreatic polypeptide (hPP). The pancreas of the mouse was divided into two lobes, the splenic and duodenal lobes, and each lobe was subdivided into three regions, the pancreatic islets (central and peripheral regions), the exocrine region and the pancreatic duct region (consisting of duct epithelium and surrounding connective tissue--sub-epithelial connective tissue). In the pancreatic islets, most of insulin-immunoreactive (IR) cells were located in the central region, and glucagon-, somatostatin and hPP-IR cells were located in the peripheral region regardless of the lobe. In the splenic part, glucagon-IR cells were also located in the central regions, and more numerous somatostatin-IR cells were detected in the central regions compared to those of the duodenal part. hPP-IR cells were restricted to the peripheral regions in both lobes but more numerous cells were detected in the duodenal portion as compared to those of the splenic portion. In the exocrine parenchyma of the splenic lobe, only insulin-, glucagon- and somatostatin-IR cells were detected.. Here, the insulin- and glucagon-IR cells formed cell clusters, while somatostatin-IR cells were present as solitary cells. In the exocrine region of the duodenal portion, only insulin-, somatostatin- and hPP-IR cells were observed, with the same distributional pattern as that found in the splenic lobe. However, clusters of cells consisting only of hPP-IR cells were distributed in the pancreas parenchyma as small islets. In the pancreatic duct region, only solitary hPP-IR cells were demonstrated in the sub-epithelial connective tissue regions of the splenic portion. In conclusion, some strain-dependent characteristic distributional patterns of pancreatic endocrine cells, especially of the hPP-IR cells, were found in the nude mouse. In addition, somewhat different distributional patterns were found between the two pancreatic lobes.     

Enzymes of the cholinergic system in islets of Langerhans.

Quantitative radiometric assays were employed to measure activities of choline acetyltransferase and acetylcholinesterase in freeze-dried pieces of islets of Langerhans and exocrine tissue from rat pancreas. The activities of both enzymes were about an order of magnitude higher in islets than in exocrine tissue. This difference in activity was found in rats made diabetic with streptozotocin as well as in the controls. Although the enzyme activities in islets from diabetic rats averaged about 30-40% higher than those in islets from control rats, the differences were statistically only marginally significant. Since the islets of diabetic rats are probably much smaller than those of control rats, it is suggested that cholinergic elements associated with pancreatic islets are lost following induction of streptozotocin diabetes.     

Impaired differentiation of endocrine and exocrine cells of the pancreas in transgenic mouse expressing the truncated type II activin receptor

Activin A is expressed in endocrine precursor cells of the fetal pancreatic anlage. To determine the physiological significance of activins in the pancreas, a transgenic mouse line expressing the truncated type II activin receptor under the control of beta-actin promoter was developed. Histological analyses of the pancreas revealed that the pancreatic islets of the transgenic mouse were small in size and were located mainly along the pancreatic ducts. Immunoreactive insulin was detected in islets, some acinar cells, and in some epithelial cells in the duct. In addition, there were abnormal endocrine cells outside the islets. The shape and the size of the endocrine cells varied and some of them were larger than islets. These cells expressed immunoreactive insulin and glucagon. In the exocrine portion, there were morphologically abnormal exocrine cells, which did not form a typical acinar structure. The cells lacked spatial polarity characteristics of acinar cells but expressed immunoreactive amylase, which was distributed diffusely in the cytoplasm. Plasma glucose concentration was normal in the transgenic mouse before and after the administration of glucose. The insulin content of the pancreas in transgenic and normal mice was nearly identical. These results suggest that activins or related ligands regulate the differentiation of the pancreatic endocrine and exocrine cells.     

A comparative study of the portal vessels connecting the endocrine and exocrine pancreas, with a discussion of some functional implications.

We have examined the pattern of the capillaries of the pancreas in rabbits, rats, mice, guinea-pigs, cats and baboons, using arterial and venous injections of Berlin blue. In all these species we found extensive, direct connexions between the capillary beds of the islets and the exocrine tissue of the gland, forming a highly developed portal system. Some of the functional implications of these vascular connexions are discussed, particularly the influence of the islet hormones insulin, glucagon and somatostatin upon the exocrine cells.     

Role of TGF-beta1 in the development of pancreatic fibrosis in Otsuka Long-Evans Tokushima Fatty rats

Recently established Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of naturally occurring obesity diabetes, exhibit progressive accumulation of connective tissue in the pancreas. The present study was designed to determine the pathogenic role of transforming growth factor-beta1 (TGF-beta1) in the development of pancreatic fibrosis in OLETF rats by investigating the serial changes in the expression of TGF-beta1 and extracellular matrix (ECM) in the pancreas. Progressive proliferation of connective tissue arose from the interstitial region surrounding islets at 20 wk of age and extended to the exocrine pancreas adjacent to the islets. TGF-beta1 mRNA levels in the pancreas increased at 20 wk of age and reached a peak value at 30 wk of age. Fibronectin (FN) and procollagen types I and III mRNAs peaked at 20 wk of age and remained at higher levels than those in the nondiabetic counterparts Long-Evans Tokushima Otsuka rats until 50 wk of age. Immunoreactivities for TGF-beta1 and FN were found in islets of OLETF rats at 20 wk of age and were seen in acinar and interstitial cells at 50 wk of age. Moreover, alpha-smooth muscle actin was located at interstitial region surrounding the islets. Proliferation of the connective tissue in the pancreas of OLETF rats closely correlated with expression of TGF-beta1 and ECM. Our results suggest that the development of pancreatic fibrosis in OLETF rats extends from endocrine to exocrine pancreas and that TGF-beta1 is involved in pancreatic fibrosis of OLETF rats.