Glandular structures in the major interlobular and extrapancreatic ducts in the guinea pig

The morphology of the pancreatic duct system did not receive much attention as compared to the microanatomy of the exocrine and endocrine pancreas. The histological peculiarities of the excretory duct system are of major importance especially in laboratory animals like guinea pigs. The paper describes the histological peculiarities of the major interlobular and extrapancreatic ducts in guinea pigs. The pancreatic tissue samples were collected from five guinea pigs. For histological investigation, several pancreatic fragments underwent fixation in 10% buffered formalin and were later processed by the standard paraffin technique. Subsequentially, tissue sections were stained by Goldner's trichrome staining. The mucous substances were assessed by Alcian blue and Periodic acid–Schiff staining methods. The interlobular and main pancreatic ducts in the guinea pig present a simple columnar epithelium surrounded by a thick layer of dense connective tissue. The aforementioned epithelium of the main pancreatic ducts includes principal cells, goblet cells and basal cells. Additionally, the ductal epithelium presents occasional unicellular multiloculated intraepithelial mucous glands and prominent extraepithelial glands. The latter adopts a simple or compound tubular feature. The mucus elaborated by the three glandular types is mostly neutral in goblet cells, predominantly acidic in extraepithelial ductal glands, and a similar amount of acidic and neutral mucin in intraepithelial glands. In conclusion, the epithelium-associated mucous glands in the interlobular and main pancreatic ducts in the guinea pig are restricted not only to goblet cells. A substantial mucous discharge probably with a protecting role against irritative pancreatic juice derives from the main ductal intraepithelial and extraepithelial glands.     

Advances in canine diabetes mellitus research: etiopathology and results of islet transplantation

Histopathologic and immunocytochemical alterations in the pancreas of 18 dogs with spontaneous diabetes mellitus were evaluated. In 5 of 18 dogs (28%), extensive pancreatic damage appeared to be responsible for the development of diabetes mellitus. In the other 13 dogs, there was substantial reduction in the number of well-granulated beta cells, but the number of well-granulated alpha and delta cells was normal in 70% and 85% of the dogs, respectively. Also, insulitis lesions composed of infiltrating mononuclear cells, predominantly lymphocytes, were observed in 6 of 13 dogs (46%), but evidence of islet-directed humoral autoimmunity was not detected. Each pancreas had dense Ia (class II antigen) expression on ductal epithelia but not on islet endocrine cells. The importance of the insulitis lesions and class II antigen expression on ductal epithelial cells remains unclear. Of the 18 dogs, 8 received multidonor intrahepatic islet allografts. Allograft rejection was prevented by administration of cyclosporin. Five dogs were administered cyclosporin continuously. One dog with an allograft failed to sustain euglycemia at 231 days after transplantation, and one dog with fasting euglycemia died of pneumonia at 186 days after transplantation. In the other dogs, euglycemia was sustained for periods that ranged from 253 to 716 days.     

Canine pancreatic endocrine tumors: immunohistochemical analysis of hormone content and amyloid

Thirty-one primary canine pancreatic endocrine tumors and their metastases were studied histologically and immunohistochemically for the presence of insulin, glucagon, somatostatin, pancreatic polypeptide (PP), gastrin, and adrenocorticotrophic hormone (ACTH). Tumors were also evaluated for the presence of amyloid. The cytoarchitectural pattern of 25 of 31 primary tumors was predominantly solid, whereas three tumors were mostly glandular, two were unclassified, and one had a gyriform pattern. Cells with insulin immunoreactivity were found in 30 of 31 tumors and were found in all cases in which there was clinical evidence of inappropriate insulin secretion. Insulin was the only hormone demonstrable in three of the 30 tumors, but cells immunoreactive for other hormones were also present in various combinations in most tumors [i.e., glucagon (13 of 30), somatostatin (17 of 30), PP (25 of 30), and gastrin (2 of 30)]. One tumor contained only cells with glucagon and PP immunoreactivity. Amyloid was found in ten of 31 primary tumors but was not detected in metastases. Cells with insulin immunoreactivity were the only cell type consistently present in tumors containing amyloid. Amyloid deposits did not immunoreact with any of the antisera. Seventeen of 31 dogs had metastasis of the pancreatic endocrine tumor to regional lymph nodes, liver, or both. All metastases available for study (15 of 17) contained cells with insulin immunoreactivity and some contained cells with PP or somatostatin immunoreactivity. No statistically significant (P greater than 0.05) differences in tendency to metastasize were found when pancreatic endocrine tumors were compared by region of origin, cytoarchitectural pattern, presence of amyloid, or by number of hormones contained within the tumor.     

Effects of melatonin on islet neogenesis and beta cell apoptosis in streptozotocin-induced diabetic rats: an immunohistochemical study

This investigation was carried out to explore the antidiabetic, antiapoptotic and neogenetic effects of melatonin (MLT) in streptozotocin-induced diabetic rats. Sixty-four male rats were assigned randomly to one of four groups for periods of 21 and 42 d as follows; i) control, ii) MLT, iii) diabetic (DM), and iv) DM + MLT. Immunohistochemical methods were used -with pancreatic tissue to determine the intensity of insulin, caspase-3 and Bcl-x(L) immune reactivities, and new islet formation. In untreated DM rats, BW loss, increased plasma glucose and MLT concentrations, as well as cytoplasmic degranulation and vacuolization were observed. We also observed a marked increase in the number of apoptotic caspase-3 positive cells and a few insulin- positive cells, but not antiapoptotic Bcl-x(L) positive cells. Observations in the DM + MLT-treated group revealed a high intensity of insulin- and antiapoptotic Bcl-x(L) immune reactivities at 21 and 42 d. Moreover, data indicated that MLT may cause beta cell proliferation and that new small islets originate from cells associated with ductal epithelium and from centroacinar cells by day 21. These data indicate that; i) MLT treatment may stimulate neogenesis in the pancreas of diabetic rats, and ii) MLT's antiapoptotic action may increase beta cell differentiation and caspase-3 inactivation or Bcl-x(L) activation.     

Localization of amylin‐like immunoreactivity in the striped velvet gecko pancreas

Immunohistochemical techniques were employed to investigate the distribution of amylin‐like immunoreactive cells in the pancreas of gecko Homopholis fasciata. Four types of endocrine cells were distinguished: insulin immunoreactive (B cells), pancreatic polypeptide immunoreactive (PP cells), glucagon and pancreatic polypeptide immunoreactive (A/PP cells) and somatostatin immunoreactive cells (D cells). Pancreatic islets contained B, A/PP and D cells, whereas extrainsular regions contained B, D and PP cells. In the pancreatic islets, amylin‐like immunoreactive cells corresponded to B cells, but not to A/PP or D cells. In the extrainsular regions, amylin‐like immunoreactive cells corresponded to either B or PP cells. Amylin secreted from intrainsular B cells may regulate pancreatic hormone secretion in an autocrine and/or a paracrine fashion. On the other hand, amylin secreted from extrainsular PP and B cells, and/or intrainsular B cells may participate in the modulation of calcium homoeostasis in an endocrine fashion.     

The prevalence of endocrinopathic laminitis among horses presented for laminitis at a first-opinion/referral equine hospital

Endocrinopathic causes of laminitis may be a common underlying causative pathogenesis in first-opinion or field cases presenting with laminitis, as opposed to laminitis produced in inflammatory research models. This study aimed to determine whether evidence of an underlying endocrinopathy was present in horses presented for laminitis to a first-opinion/referral veterinary teaching hospital. A second aim was to compare the signalment of horses and ponies with laminitis with the equine hospital population during the same period. All horses presenting for laminitis at Helsinki University Equine Teaching Hospital, Finland, over a 16-month period were examined for an underlying endocrinopathy. Horses presenting for laminitis were compared with the hospitalized population over the same period. There were 36 horses presented for laminitis, and evidence of endocrinopathy was present in 89%. Of the horses showing an underlying endocrinopathy, one-third had a diagnosis of pituitary pars intermedia dysfunction, and two-thirds showed basal hyperinsulinemia indicative of insulin resistance, without evidence of hirsutism. Phenotypic indicators of obesity were present in 95% of horses with basal hyperinsulinemia without hirsutism. Compared with the hospital population during the same period, horses with laminitis associated with an underlying endocrinopathy were significantly older and more likely to be pony breeds. Our data support that endocrine testing should be performed on all cases of laminitis that do not have a clear inflammatory or gastrointestinal origin.     

Proportions of various endocrine cells in the pancreatic islets of wood mice (Apodemus speciosus)

Using wood mice (Apodemus speciosus) captured in the wild in Niigata, we analysed the proportion of various endocrine cells in pancreatic islets for both immunohistochemical and microscopic characteristics. In both the dorsal and ventral portions of the pancreas, the centre of the pancreatic islets was occupied predominantly by insulin-positive (B) cells, surrounded by glucagon-positive (A), somatostatin-positive (D), and pancreatic-polypeptide-positive (PP) cells. Although the proportions of the various endocrine cells in pancreatic islets varied from one mouse to the next, in most animals B cells accounted for more than half of all endocrine cells. Dorsal and ventral portions of the pancreas differed in the proportions of various endocrine cells, specifically, in the A-to-PP cell ratio: the proportion of PP cells higher in the ventral portion. The same tendency is seen in humans, rats and mice. Microscopic examinations revealed morphologically distinct secretory granules in A, B and D cells. The morphology of these granules was similar that of secretory granules found in rats and mice.     

Pancreatic injury in equine acute abdomen evaluated by plasma trypsin activity and histopathology of pancreatic tissue

In cases of equine acute abdominal disease, where pancreatic damage is suspected, pancreatic damage can be assessed by measuring increased trypsin activity in the plasma of horses suffering intestinal obstruction and severe shock. The pancreas is particularly vulnerable to splanchnic hypoperfusion because it is a highly active tissue. In this study, 10 horses undergoing abdominal surgery for intestinal obstruction were assayed for trypsin activity on admission and, because of extensive intestinal lesions that were not amenable to surgery, euthanasia was selected; the pancreas was removed before euthanasia. Trypsin activity in the plasma of these horses was significantly higher than in healthy horses (196 ng/ml +/- 128.2 versus 28.5 ng/ml +/- 19.2; P = 0.0026). Light and transmission electron microscopy revealed slight to severe lesions of vacuolar degeneration, a few zymogen granules, dilation of the endoplasmic reticulum, and swelling of mitochondria in the exocrine pancreas. The activation of an inflammatory cascade occurring during strangulating intestinal obstruction could increase pancreatic anoxic lesions caused by severe shock and hypoperfusion in the horse. Further studies will show the significance of pancreatic lesions and the ensuing damage in equine acute intestinal obstruction and shock.     

Endocrine-paracrine cells of the male urogenital apparatus: a comparative histochemical and immunohistochemical study in some domestic ungulates

Specimens of testis, excurrent duct including the male accessory glands and urethra, were studied in boars, bulls, horses and donkeys, in order to localize endocrine/paracrine cells. Silver impregnation methods were used to test the argentaffinity and/or argyrophilia of cells. Immunoreactivities to chromogranin A, 5-hydroxytryptamine, somatostatin, [met]- and [leu]- enkephalins, gastrin-releasing peptide, calcitonin gene-related peptide, neuropeptide Y, substance P, vasoactive intestinal peptide, beta-endorphin antisera were tested by a streptavidin-biotin method. In the testis, epididymis, ductus deferens and vesicular gland no endocrine cells were found in any of the animals studied. Chromogranin-A, serotonin, somatostatin and enkephalins were present in endocrine/paracrine cells in the surface or glandular epithelia, whereas all other antisera gave negative results. In the prostatic complex and the urethral epithelium, the most consistent number of endocrine cells was serotonin-immunoreactive. Few cells were also argentaffin and a very limited number of them showed argyrophily and chromogranin-A immunoreactivity. Somatostatin-and enkephalin-immunoreactive cells were rare in the bull and boar, absent in stallions. This comparative study carried out on different species of domestic ungulates has shown deeply different immunophenotypes, even comparing species that are in a very close zoological relationship with one another, such as the horse and the donkey.     

Superficial necrolytic dermatitis and a pancreatic endocrine tumour in a dog

A 13-year-old dog was referred for a severe dermatological problem of 12 months duration. Skin biopsy results were compatible with superficial necrolytic dermatitis. The only laboratory abnormalities were hyperglycaemia and hyperglucagonaemia. These findings suggested a pancreatic endocrine tumour in association with superficial necrolytic dermatitis. Abdominal ultrasound examination was unremarkable. The dog was euthanased due to the lack of clinical improvement following symptomatic therapy. Postmortem examination revealed a pancreatic endocrine tumour with liver metastases. Pancreatic endocrine tumour cells were immunoreactive for glucagon, insulin and islet amyloid polypeptide.     

An investigation of the relationship between duct system and A cell-rich and PP cell-rich pancreatic islets in the canine pancreas.

The pancreata of four six-month-old dogs of the same mother, two with both the pancreatic and accessory pancreatic ducts (X-type) and two with only the accessory pancreatic duct (Y-type), were examined in this study. To clarify the relationships between the type of pancreatic duct system and the composition of pancreatic endocrine cells, the pancreata were examined immunohistochemically using antiserum against four types of pancreatic hormones (glucagon, insulin, somatostatin and pancreatic polypeptide). In all areas of the X- and Y-type duct system pancreata, B cells accounted for 52-82% of the total number of islet cells, and D cells accounted for 4-15%. In the X-type ducts system, the percentages of A and PP cells in the right and left lobes of the pancreas differed greatly. It was found that A and PP cells appear in inverse proportion to each other and that there exist A cell-rich and PP cell-rich pancreatic islets. The A cell-rich pancreatic islets appeared in the left lobes along the accessory pancreatic duct, while the PP cell-rich pancreatic islets were observed in the right lobes along the pancreatic duct. The body of the pancreas contained both A cell-rich and PP cell-rich pancreatic islets. In the Y-type duct systems, A cell-rich pancreatic islets appeared in the right lobes. These findings indicate that the composition of A and PP cells in pancreatic islets is closely related to the type of duct system.     

Clinical, immunophenotypic and functional characterisation of T-cell leukaemia in six horses

REASON FOR PERFORMING STUDY: Lymphoid leukaemia (LL) is rare in equids. In man, immunophenotypic classification identifies distinct leukaemic types with different treatment strategies. Improved understanding and classification of equine LL may allow similar advances. OBJECTIVES: To document the clinical, immunophenotypic and functional characteristics in 6 cases of equine LL of T-cell origin. METHODS: The clinical records and pathological findings from 6 cases of equine LL were analysed. Immunohistochemistry to identify T or B lymphocytes was performed on paraffin embedded tissues in 4 cases. Peripheral blood mononuclear cells (PBMC) were phenotyped for expression of CD4, CD8, MHC class I and II and B-cell antigens in 4 cases using monoclonal antibodies (mAbs) and flow cytometry. Neoplastic lymphocytes from 4 horses were stimulated with mitogens. RESULTS AND CONCLUSIONS: Six horses of various breeds were identified with LL of T-cell origin. The clinical course and presenting signs varied. Neoplastic lymphocytes were identified in peripheral blood samples from all horses and tissue invasion was confirmed at examination post mortem in 4 horses. Immunophenotyping identified a predominance of CD3+ T-cells in lymphoid tissues and CD4+ T-cells in circulating peripheral blood mononuclear cells (PBMC) in the affected horses. Neoplastic lymphocytes from the 4 cases that were tested failed to proliferate in response to mitogens. POTENTIAL RELEVANCE: Characterisation of the clinical, pathological and immunological findings in 6 horses with LL has added to reports of this rare condition, characterised it in greater detail and therefore provides a starting point for further investigations.     

Equine giant cell tumor of soft parts: a series of 21 cases (2000-2007).

In horses, giant-cell tumors of soft parts are rare neoplasms, with the majority of reported cases occurring within the hind limb muscles and soft tissues in older horses. The following article documents 21 cases of equine giant-cell tumors of soft parts clinically examined within the state of Colorado from 2000 to 2007. The majority of cases occurred in male horses aged 10 years or older. Nine (43%) arose within the hind limbs. Key histologic features included numerous multinucleated giant cells and hemosiderin-laden macrophages admixed with a spindle-cell proliferation. The majority demonstrated liposarcomatous change, variable areas of necrosis and hemorrhage, and an intermediate number of mitotic figures. Immunohistochemical results demonstrated 2 distinct cell populations: vimentin-expressing neoplastic mesenchymal cells and CD18 (histiocytic marker) expressing multinucleated giant cells. These results suggest a mesenchymal origin of the neoplasm with possible recruitment of the secondary histiocytic population. Surgical excision was attempted in the majority of horses and was considered clinically complete. A recurrence of the neoplasm was documented in 1 horse and 1 mule. In 18 horses, surgical excision, regardless of margin integrity, appeared successful with no recurrence of disease documented. Unfortunately, 10 of 21 horses were lost to follow-up within approximately 3 months of surgery. Of the 11 remaining horses that were available for follow-up evaluation, there has been no evidence of metastasis. A larger case series with more controlled follow-up is necessary to evaluate malignant potential and the importance of complete surgical excision.     

Morphologic and immunocytochemical study of young dogs with diabetes mellitus associated with pancreatic islet hypoplasia

In 11 dogs (7 males, 4 females; 10 purebred, 1 mixed breed), diagnosed as having diabetes mellitus before the age of 6 months, the pancreas was evaluated histologically; in 6, the pancreas also was examined by use of electron microscopy and/or immunocytochemical methods. Each dog was placed in 1 of 3 groups (A through C) on the basis of pancreatic histopathologic findings: Group A (n = 3)--no recognizable islets, but the pancreas in 2 dogs contained scattered endocrine cells detectable by use of immunoperoxidase staining or electron microscopy; Group B (n = 4)--no recognizable islets, but the pancreas had severe vacuolation of ducts and acini, as well as acinar atrophy; Group C (n = 4)--scant shrunken islets; 1 pancreas had reduced numbers of recognizable islets, hydropic beta-cell vacuolation attributable to glycogen deposition, and islet and nonislet endocrine cells in expected proportions. Insulitis was not observed in any pancreas, although scattered lymphocytes were seen in the pancreatic interstitial fibrous tissue of 3 dogs. Histologic pancreatic lesions in these young dogs were distinct from those of type-I (insulin-dependent) diabetes mellitus in human beings, as well as from those of diabetes mellitus in aged dogs, but were similar to those described in other young diabetic dogs. This uncommon syndrome is distinct from commonly recognized canine diabetes mellitus, on the basis of age of onset, predisposition for purebred dogs, lack of predisposing endocrinopathies or obesity, and pancreatic histologic features. The cause(s) is unknown, but is related to pancreatic endocrine hypoplasia and not to insulitis or to exocrine pancreatic inflammation. The term pancreatic islet hypoplasia is chosen as best describing this disorder.     

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.     

An immunohistochemical study of endocrine cells in the alimentary tract of the red-bellied frog, Bombina orientalis

The regional distribution and relative frequency of endocrine cells was studied immunohistochemically (PAP method) in the alimentary tract of the red-bellied frog, Bombina orientalis, using antisera against serotonin, somatostatin, chromogranin (CG), cholecystokinin (CCK)-8, bombesin, secretin, glucagon and pancreatic polypeptide (PP). Eight kinds of endocrine cells were identified in this study. These immunoreactive cells were located in the gastric glands of the stomach regions and in the intestinal or esophageal epithelium with variable frequencies. They were spherical or spindle-shaped. Serotonin- and somatostatin-immunoreactive cells were demonstrated in the whole alimentary tract including esophagus. CG-immunoreactive cells were restricted to the stomach. CCK-8-immunoreactive cells were observed from the antrum to the ileum. Bombesin-immunoreactive cells were restricted to the stomach. Secretin-immunoreactive cells were demonstrated in the pylorus, duodenum and ileum. Glucagon-immunoreactive cells were found in the antrum and duodenum. PP-immunoreactive cells were detected from the antrum to the rectum. In conclusion, throughout the alimentary tract of the red-bellied frog, the different regional distribution and relative frequency of endocrine cells were demonstrated. The regional distributions and relative frequencies of the endocrine cells in the alimentary tract of the red-bellied frog were resembled to those of the other anuran species except for esophagus.     

Simultaneous occurrence of multiple neoplasms and hyperplasias in the adrenal and thyroid gland of the horse resembling multiple endocrine neoplasia syndrome: case report and retrospective identification of additional cases

Neoplastic and hyperplastic disorders that affect multiple endocrine tissues in a single individual are well described in humans but less so in domestic animals. Multiple endocrine neoplasia (MEN) in humans is a genetically determined syndrome characterized by the appearance of benign or malignant proliferations within two or more endocrine glands. The primary endocrine tumors that are characteristic of MEN arise from cells that share the capacity for amine precursor uptake and decarboxylation. Here we describe the case of a 22-year-old Thoroughbred mare that died during an unattended parturition and subsequently was presented for necropsy at the University of California, Davis, Veterinary Medical Teaching Hospital. A C-cell (medullary) thyroid adenoma, pheochromocytoma, and multicentric bilateral nodular hyperplasia of the adrenal medulla were present, findings that are remarkably similar to those of human MEN syndrome. Mortality during pregnancy in women with undiagnosed pheochromocytoma is high (approximately 50%), typically because of hypertension and/or hemorrhage associated with catecholamine release from the tumor. Similarly, the mare in this report died of hemorrhage subsequent to parturition. A retrospective evaluation of endocrine tumors in horses that underwent necropsy at the Veterinary Medical Teaching Hospital from 1987 to 1997 was undertaken to identify additional possible cases of MEN in horses. Data from this retrospective evaluation suggest that coexistence of hyperplasias and neoplasias of the thyroid and adrenal glands, similar to MEN syndrome of humans, also occurs with some frequency in the horse.     

Digestive enzyme concentrations and activities in healthy pancreatic tissue of horses

OBJECTIVE: To measure concentrations and activities of major digestive enzymes in healthy equine pancreatic tissue. ANIMALS: 7 adult horses with normal pancreatic tissues. PROCEDURES: Small pieces of pancreatic tissue were collected immediately after euthanasia, immersed in liquid nitrogen, and maintained at -80 degrees C until analyzed. Concentrations and activities of amylase, lipase, chymotrypsin, trypsin, and elastase were determined by use of a microtiter technique. Relative pancreatic protein concentrations were determined by use of bovine serum albumin as the standard. Pancreatic DNA was extracted and con-centrations determined by use of the diphenylamine method with calf thymus DNA as the standard. RESULTS: The pancreatic cellular concentration of each enzyme, expressed as units per milligram of DNA, was consistent among horses. Cellular concentration of lipase (1,090.8 +/- 285.3 U/mg of DNA) was highest, followed by amylase (59.5 +/- 9.8 U/mg of DNA). Elastase, trypsin, and chymotrypsin were detected in small concentrations (1.9 +/- 0.6, 3.5 +/- 1.5, and 9.6 +/- 2.9 U/mg of DNA, respectively). Similar results were obtained for specific activities of the enzymes. CONCLUSIONS AND CLINICAL RELEVANCE: Results were unexpected because, under natural conditions, the predominant energy source for horses is carbohydrate. These results may indicate, in part, the reason horses seem to tolerate large amounts of fat added to their diet.     

Expression of claudin-5 in canine pancreatic acinar cell carcinoma - An immunohistochemical study

Claudin-5 is an endothelium-specific tight junction protein. The aim of the present study was to detect the expression pattern of this molecule in intact pancreatic tissues and in well-differentiated and poorly differentiated pancreatic acinar cell carcinomas from dogs by the use of cross-reactive humanised anticlaudin-5 antibody. The necropsy samples taken from dogs included 10 nonneoplastic pancreatic tissues, 10 well-differentiated pancreatic acinar cell carcinomas, 10 poorly differentiated pancreatic acinar cell carcinomas, 5 intrahepatic metastases of well-differentiated and 5 intrahepatic metastases of poorly differentiated acinar cell carcinomas. A strong lateral membrane claudin-5 positivity was detected in exocrine cells in all intact pancreas samples. The endocrine cells of the islets of Langerhans and the epithelial cells of the ducts were negative for claudin-5. The endothelial cells of vessels and lymphatic channels in the stroma of the intact pancreas showed strong membrane positivity for this claudin. All well-differentiated exocrine pancreas carcinomas and all poorly-differentiated pancreatic acinar cell carcinoma samples showed a diffuse loss of claudin-5 expression. The claudin-5-positive peritumoural vessels and lymphatic channels facilitated the detection of vascular invasion of the claudin-5-negative cancer cells. In liver metastasis samples, the pancreatic carcinomas were negative for claudin-5. It seems that the loss of expression of claudin-5 may lead to carcinogenesis in canine exocrine pancreatic cells.     

Microanatomic features of pancreatic islets and immunolocalization of glucose transporters in tissues of llamas and alpacas

OBJECTIVE: To describe the microanatomic features of pancreatic islets and the immunohistochemical distribution of glucose transporter (GLUT) molecules in the pancreas and other tissues of New World camelids. ANIMALS: 7 healthy adult New World camelids, 2 neonatal camelids with developmental skeletal abnormalities, and 2 BALB/c mice. PROCEDURE: Samples of pancreas, liver, skeletal muscle, mammary gland, brain, and adipose tissue were collected postmortem from camelids and mice. Pancreatic tissue sections from camelids were assessed microscopically. Sections of all tissues from camelids and mice (positive control specimens) were examined after staining with antibodies against GLUT-1, -2, -3, and -4 molecules. RESULTS: In camelids, pancreatic islets were prominent and lacked connective tissue capsules. Numerous individual endocrine-type cells were visible distant from the islets. Findings in neonatal and adult tissues were similar; however, the former appeared to have more non-islet-associated endocrine cells. Via immunostaining, GLUT-2 molecules were detected on pancreatic endocrine cells and hepatocytes in camelids, GLUT-1 molecules were detected on the capillary endothelium of the CNS, GLUT-3 molecules were detected throughout the gray matter, and GLUT-4 molecules were not detected in any camelid tissues. Staining characteristics of neonatal and adult tissues were similar. CONCLUSIONS AND CLINICAL RELEVANCE: In New World camelids, microanatomic features of pancreatic islets are similar to those of other mammals. Data suggest that the poor glucose clearance and poor insulin response to hyperglycemia in adult camelids cannot be attributed to a lack of islet cells or lack of GLUT molecules on the outer membrane of those cells.