Morphometric and immunohistochemical study on the endocrine cells of pancreatic transplants

The effect of a fat-enriched diet on the pattern of distribution of pancreatic islet cells in the C57BL/6J mice

The C57BL/6J mice are inbred strains and develop the metabolic syndrome of obesity, hyperinsulinemia, hyperglycemia, and hypertension, when fed a high-fat diet. These features are similar to those observed in the human metabolic syndrome. This article examined the effect of fat-enriched (FE) diet on the pattern of distribution of insulin-, glucagon-, somatostatin-, and pancreatic polypeptide (PP)-positive cells in the pancreatic islets of C57BL/6J mice using immunohistochemical methods. Insulin-immunoreactive cells were observed in both the peripheral and central regions of the islets of Langerhans in both FE- and control diet-fed mice. The percentage distribution of insulin-positive cells was similar in FE (83.5 +/- 6.4) compared to control diet-fed C57BL/6J mice (83.8 +/- 6.5). Glucagon-containing cells were discerned in the periphery of pancreatic islets in both FE- and control diet-fed mice. The percentage distribution of glucagon was not statistically different in mice fed with FE (9.9 +/- 2.7) compared to control diet (11.3 +/- 4.9). Somatostatin-positive cells were seen in the outer part of the islet of Langerhans and constitute 12.1% (+/-6.3) and 10% (+/-5.5) of pancreatic islet cells in FE- and control diet-fed mice, respectively. PP-immunoreactive cells were observed in the peripheral region of the pancreatic islets of both FE- and control diet-fed mice. The percentage distribution of PP-positive cells was significantly (2.0 +/- 1.2) lower compared to control (5.1 +/- 2.4). In conclusion, the number of PP is significantly reduced in FE diet-fed mice and may play a role in the pathogenesis of diet-induced metabolic syndrome in C57BL/6J mice.

Distribution of vasoactive intestinal polypeptide, neuropeptide-Y and substance P and their effects on insulin secretion from the in vitro pancreas of normal and diabetic rats

This study examined the pattern of distribution of vasoactive intestinal polypeptide (VIP), neuropeptide-Y (NPY) and substance P (SP) in the pancreas of diabetic rat to determine whether there are changes in the number and pattern of distribution of these neuropeptides after the onset of diabetes. Moreover, the effect of VIP, NPY and SP on insulin secretion from the pancreas of normal and diabetic rats was also examined. Diabetes mellitus (DM) was induced by a single dose of streptozotocin (STZ) given intraperitoneally (i.p.) (60 mg kg body weight(-1)). Four weeks after the induction of DM, diabetic (n = 6) and normal (n = 6) rats were anesthetized with chloral hydrate and their pancreases removed and processed for immunohistochemistry and insulin secretion. The number of insulin-positive cells in the islets of Langerhans was reduced while that of VIP and NPY increased significantly after the onset of diabetes. The pattern of distribution of VIP, NPY and SP in the nerves innervating the pancreas was similar in both normal and diabetic rats. VIP-evoked large and significant (P < 0.02) increases in insulin secretion from the pancreas of normal and diabetic rats. NPY also induced a marked (P < 0.005) increase in insulin release from pancreatic tissue fragments of normal rat. Stimulation of pancreatic tissue fragments of diabetic rat with NPY resulted in a slight but not significant increase in insulin release. SP induced a large and significant (P < 0.005) increase in insulin secretion from the pancreas of normal rat but inhibited insulin secretion significantly (P < 0.03) from isolated pancreas of diabetic rat. In summary, VIP and NPY can stimulate insulin secretion from the pancreas after the onset of diabetes. The stimulatory effect of SP on insulin secretion is reversed to inhibitory in diabetic rats.

Distribution of NPY and SP and their effects on glucagon secretion from the in vitro normal and diabetic pancreatic tissues

Neuropeptides modulate the function of classic neurotransmitters in the regulation of body function. The role of neuropeptides in the regulation of endocrine secretion from the pancreas of diabetic rat is poorly understood. This study examined the pattern of distribution of neuropeptide-Y (NPY) and substance P (SP) in normal and diabetic rat pancreases. In addition to this, the effect of NPY and SP on glucagon secretion was also examined in the pancreases of normal and diabetic rats. Four weeks after the induction of diabetes, the pancreaseses of normal and diabetic rats were removed and processed for immunohistochemistry and glucagon secretion. The pattern of distribution of glucagon in the pancreas of diabetic rat was conspicuously deranged after the onset of diabetes. The pattern of distribution of NPY and SP was, however, similar in the pancreases of both normal and diabetic rats. Stimulation of normal rat pancreatic tissue with NPY (10(-12) and 10(-9) M) evoked large and significant (P < 0.001) increases in glucagon secretion compared to basal. In contrast to this, NPY inhibited glucagon secretion from the pancreas of diabetic rat. Treatment of pancreatic tissue fragments of normal rat with 10(-9) M SP resulted in significant (P < 0.03) increases in glucagon secretion. SP inhibited glucagon secretion from diabetic rat pancreas. In conclusion, NPY and SP stimulated glucagon secretion from the pancreas of normal rat. In contrast, NPY and SP inhibited glucagon secretion from diabetic rat pancreas.

Distribution of calcitonin-gene-related peptide, neuropeptide-Y, vasoactive intestinal polypeptide, cholecystokinin-8, substance P and islet peptides in the pancreas of normal and diabetic rats

Neuropeptides and peptides are particularly important in the co-ordination of pancreatic exocrine and endocrine secretions. In diabetes mellitus, pancreatic endocrine secretion is particularly impaired. This study investigates whether there is a change in the pattern of distribution of neuropeptides including calcitonin-gene-related peptide (CGRP), neuropeptide-Y (NPY), vasoactive intestinal polypeptide (VIP), cholecystokinin-octapeptide (CCK-8), substance P (SP), and islet peptides including insulin (INS), glucagon (GLU), somatostatin (SOM) and pancreatic polypeptide (PP) in the pancreas of streptozotocin (STZ)-diabetic rats. After the onset of diabetes, the pattern of distribution of INS, GLU, SOM and PP cells was deranged. CGRP was demonstrated in ganglion cells of both normal and diabetic pancreas. CGRP was also localized in nerve fibres innervating the blood vessels of both normal and diabetic pancreas. The pancreata of both normal and diabetic rats contained numerous NPY-immunopositive varicose nerve fibres in the wall of blood vessels. In normal pancreatic tissue, VIP-immunopositive nerve fibres were observed in all areas of the pancreas. After the onset of diabetes, VIP-positive nerve fibres were still discernible in the interacinar regions of the pancreas. CCK-8 was identified in nerve fibres innervating both the normal and diabetic rat pancreata. These CCK-8-immunopositive nerves were varicose in nature and distributed in the wall of blood vessels. SP was demonstrated in neurons located in the interlobular areas of normal tissue and in fine varicose nerve fibres of the interacinar region of STZ-induced diabetic pancreas. In conclusion, CGRP, NPY, VIP, CCK-8 and SP are well distributed in both normal and diabetic pancreas.

Host-graft circulation and vascular morphology in pancreatic tissue transplants in rats

One of the most determining factors for the survival of tissue grafts is an intact vasculature. This vasculature must, however, be linked to the circulation of the host animals for survival and growth to occur. The mechanism(s) of revascularization of pancreatic tissue grafts is still unclear and more so the process by which the host blood vessels anastomose with those of the graft. The microvasculature and revascularization of neonatal pancreatic tissue fragments transplanted into the anterior eye chamber of rats were investigated using conventional light and electron microscopy as well as the india ink perfusion method. Light microscopy demonstrated that the blood vessels of the host iris revascularized the transplants within 24 h of transplantation. Sinusoidal blood capillaries were observed to invade the peripheral parts of the grafts. The capillary encroachment from the iris into the graft continued through the second day of transplantation. The host-graft anastomosis developed completely and became prominent and conspicuous after the third day of transplantation. Many capillaries were observed to encroach into the graft from the iris. The vasculature of the graft was increased in comparison with that of normal pancreatic tissue. This increase was prominent especially around pancreatic islet and ductal cells which survived after transplantation. Blood cells observed in these vessels of the graft indicated a functional state. The ultrastructure of the intrinsic blood vessels of the graft was intact and showed the peculiar fenestrations normally seen in the blood vessels of endocrine tissues. These observations indicated that pancreatic tissue fragments transplanted into the anterior eye chamber of rats were revascularized within 24 h. The revascularization was completed at the end of the third day of transplantation when definitive blood vessels linked the circulation of the graft with that of the iris.

Effects of Momordica charantia fruit juice on islet morphology in the pancreas of the streptozotocin-diabetic rat

An investigation was made of the effect of Momordica charantia fruit juice on the distribution and number of alpha, beta and delta cells in the pancreas of streptozotocin (STZ)-induced diabetic rats using immunohistochemical methods. The results indicated that there was a significant (Student's t-test, P < 0.004) increase in the number of beta cells in M. charantia-treated animals when compared with untreated diabetics, however, their number was still significantly less than that obtained for normal rats. There was also a significant (P < 0.006) increase in the number of delta cells in STZ-diabetic rats compared to non-diabetic rats. This increase in the number of delta cells was not affected by M. charantia treatment. The number of alpha cells did not change significantly in M. charantia-treated rats when compared with untreated diabetic rats. Our results suggest that oral feeding of M. charantia fruit juice may have a role in the renewal of beta cells in STZ-diabetic rats or alternately may permit the recovery of partially destroyed beta cells.

Immunohistochemical identification of pancreatic hormones, neuropeptides and cytoskeletal proteins in pancreas of the camel (Camelus dromedarius)

The patterns of distribution of insulin (INS), glucagon (GLU), atrial natriuretic peptide (ANP), neuropeptide-Y (NPY), cholecystokinin-octapeptide (CCK-8), neurofilament-200 protein (NF), S-100 protein (S-100), and vimentin (VIM) in the pancreas of the one-humped camel (Camelus dromedarius) were investigated using immunohistochemical techniques. INS-immunoreactive cells were observed in the central and peripheral parts of the islets of Langerhans, but some solitary INS-positive cells were found outside the islets. INS-positive cells constituted 44.26-90.91% [mean +/- standard deviation (std): 67.34 +/- 14.20] of the total number of islet cells. GLU-immunopositive cells were located mainly in the peripheral region of the islets, and they constituted 11.43-44.44% [mean +/- std: 23.54 +/- 8.27] of the total number of islet cells. ANP and CCK-8 immunoreactivity was observed in neurons and perivascular nerves fibers. NPY was identified in pancreatic neurons and in some peripheral and central cells of the islets of Langerhans. VIM immunoreactivity was observed in the endothelial cells of blood vessels and the nerves located in the perivascular, interlobular and periacinar regions. VIM was also detected immunohistochemically in the periductal nerves of the pancreas. NF occurred only in nerves. S-100 was discerned mainly in the nerves of the interlobular connective tissue and in nerves lying close to blood vessels and acinar tissue. It is concluded that INS, GLU, ANP, NPY, CCK-8, NF, S-100, and VIM are well distributed in the pancreas of the camel.

Interactions of islet hormones with acetylcholine in the isolated rat pancreas

This study investigates the effects of the islet hormones, insulin (INS), glucagon (GLU) and somatostatin (SOM) on acetylcholine (ACh)-evoked amylase secretion and calcium (Ca2+) mobilization in the isolated rat pancreas. Stimulation of pancreatic segments and acini with either INS, GLU or SOM resulted in small increases of amylase output compared to much large increases in enzyme output with ACh. Combinations of the peptide hormones with ACh resulted in enhanced secretory responses compared to the effects obtained with either ACh or each of the islet hormone alone. Genistein, the tyrosine kinase inhibitor, evoked a decrease in amylase output from pancreatic segments. It had no effect on the ACh evoke secretory response but it markedly inhibited the potentiation of the islet hormones with ACh. In pancreatic acinar cells either INS, GLU or SOM elicited moderate increases in amylase output compared to much larger responses with ACh. Furthermore, the islet hormones failed to potentiate the secretory effect of ACh in pancreatic acini. In fura-2 AM loaded acinar cells both INS and GLU evoked small increases in intracellular free calcium concentration [Ca2+]i compared to a much larger elevation with ACh. Both INS and GLU enhanced the ACh-evoked [Ca2+]i. Genistein elicited a decrease in [Ca2+]i both in the absence and presence of both INS and GLU. It also decreased the rise in [Ca2+]i resulting from the combined presence of ACh with both INS and GLU. SOM had no significant effect on the ACh-induced [Ca2+]i. When genistein was combined with ACh and SOM there was a decrease in [Ca2+]i compared to the response obtained with SOM and ACh alone. The results indicate that both tyrosine kinase and cellular Ca2+ seem to be the intracellular mediators associated with the enhanced secretory responses obtained with a combination of the islet hormones with ACh. Finally, our results using immunohistochemical techniques confirm the presence of INS-, GLU- SOM- and ACh-immunoreactive cells in the endocrine and neural elements of the rat pancreas.