Pancreas Research Papers - Academia.edu (original) (raw)

Fluorescent fusion proteins are an important tool for the study of vesicle trafficking and exocytosis, especially when combined with newer types of microscopy. We previously reported that the design of a vesicle-targeted fluorescent... more

Fluorescent fusion proteins are an important tool for the study of vesicle trafficking and exocytosis, especially when combined with newer types of microscopy. We previously reported that the design of a vesicle-targeted fluorescent fusion construct strongly influences the kinetics of fluorescence change at exocytosis. In the present study we demonstrate that the cell in which a construct is expressed also affects the kinetics of fluorescence change at exocytosis. We fused enhanced green fluorescent protein to the carboxy terminus of the vesicular cargo protein rodent islet amyloid polypeptide. The two proteins were separated by a “linker” sequence of 18 amino acids. We then compared kinetics of fluorescence change at exocytosis for this fluorescent cargo protein expressed in three different types of peptidergic endocrine cell: pancreatic alpha cell, pancreatic beta cell, and adrenal chromaffin cell. In resting cells of all three types, fluorescent spots of similar size and membrane-proximal density appeared near the plasma membrane as expected if the probe is stored in large dense-core secretory vesicles. Upon stimulation, the fluorescent spots displayed sudden changes in fluorescence intensity that were consistent with exocytosis. In beta and alpha cells the fluorescent spots consistently brightened and persisted, whereas in chromaffin cells the fluorescent spots always dispersed rapidly. Thus, for fluorescent cargo proteins in peptidergic endocrine cells, cell type influences the kinetics of fluorescence change at exocytosis. Together with our previous findings, this observation strongly highlights the fact that the behavior of vesicle-targeted fluorescent cargo may be unrelated to that of native cargo, and it emphasizes the need for caution in interpreting fluorescence kinetics in terms of an exocytosis mechanism.

The aim of this study was to evaluate the negative effects of the Pringle maneuver on pancreatic tissue with respect to the time of performing the maneuver. Moreover, the efficacy of octreotide therapy on pancreatic changes at the time of... more

The aim of this study was to evaluate the negative effects of the Pringle maneuver on pancreatic tissue with respect to the time of performing the maneuver. Moreover, the efficacy of octreotide therapy on pancreatic changes at the time of the Pringle maneuver was assessed. Fifty male Wistar Albino rats were randomized into 5 groups. The groups were formed as follows: Group A: sham operation, Group B: Pringle maneuver for 30 min plus octreotide (PM30-OCT), Group C: Pringle maneuver for 60 min plus octreotide (PM60-OCT) and Group D: Pringle maneuver for 30 min plus 0.9 % saline solution (PM30-SS), Pringle maneuver for 60 min plus 0.9 % saline solution (PM60-SS, Group E). Blood samples for the evaluation of both amylase and lipase levels were taken via the portal vein. Levels of glutathione, glutathione reductase, catalase, myeloperoxidase, nitric oxide, xanthine oxidase, malondialdehyde, tumour necrosis factor alpha (TNF-alpha), and interleukin-1 beta (IL-1 beta) were assessed in the ...

The influence of CCK-A receptor antagonism on pancreatic exocrine secretion and duodenal EMG, and the mechanism(s) involved in CCK-induced pancreatic secretion were studied in conscious calves. Seven 1-week-old calves were fitted with a... more

The influence of CCK-A receptor antagonism on pancreatic exocrine secretion and duodenal EMG, and the mechanism(s) involved in CCK-induced pancreatic secretion were studied in conscious calves. Seven 1-week-old calves were fitted with a pancreatic duct catheter, duodenal cannula and duodenal electrodes. Pancreatic exocrine secretion and duodenal EMG were studied following intraduodenal CCK-A receptor antagonist (Tarazepide), intravenous atropine, and intravenous or intraduodenal CCK-8 administrations. Tarazepide decreased duodenal electric activity, reduced interdigestive pancreatic secretion, especially protein; reduced cephalic and early postprandial (milk) induced secretion of bicarbonate and protein. Pancreatic protein secretion to intravenous CCK-8 was little affected by atropine, but was significantly reduced by Tarazepide+/-atropine; in contrast, protein secretion to intraduodenal CCK-8 was abolished by Tarazepide or atropine. We conclude that pre- and especially early postpr...

Abstract: The pancreas is highly susceptible to the oxidative stress induced by ischemia/reperfusion (IR) injury leading to the generation of acute pancreatitis. Melatonin has been shown to be useful in the prevention of the damage by... more

Abstract: The pancreas is highly susceptible to the oxidative stress induced by ischemia/reperfusion (IR) injury leading to the generation of acute pancreatitis. Melatonin has been shown to be useful in the prevention of the damage by ischemia-reperfusion in liver, brain, myocardium, gut and kidney. The aim of the study was to evaluate the cytoprotective properties of melatonin against injury induced by IR in pancreas. The obstruction of gastro-duodenal and inferior splenic arteries induced pancreatic IR in male Wistar rats. Melatonin was intraperitoneally administered before or/and after IR injury. The animals were killed at 24 and 48 hr after reperfusion and there were evaluated parameters of oxidative stress (lipoperoxides, superoxide dismutase, catalase, glutathione peroxidase and reduced glutathione), glandular endocrine and exocrine function (lipase, amylase, insulin) and cell injury (apoptosis and necrosis). The IR induced a marked enhancement of oxidative stress and impaired pancreatic function. The histological analysis showed that IR induced acute pancreatitis with the accumulation of inflammatory infiltrate, disruption of tissue structure, cell necrosis and hemorrhage. Melatonin administration before or after pancreatic IR prevented all tissue markers of oxidative stress, biochemical and histological signs of apoptosis and necrosis, and restored glandular function. No histological signs of pancreatitis were observed 48 hr after reperfusion in 80% of the animals treated with melatonin, with only a mild edematous pancreatitis being observed in the remaining rats. Preventive or therapeutic administration of melatonin protected against the induction of oxidative stress and tissue injury, and restored cell function in experimental pancreatic IR in rats.

Chronic pancreatitis is a severe inflammation of the pancreas associated with destruction of the parenchyma, fibrosis, and persistent abdominal pain. Cyclooxygenase-2 (COX-2) and COX-2-derived prostaglandins, key mediators of the... more

Chronic pancreatitis is a severe inflammation of the pancreas associated with destruction of the parenchyma, fibrosis, and persistent abdominal pain. Cyclooxygenase-2 (COX-2) and COX-2-derived prostaglandins, key mediators of the inflammatory response, are elevated in patients with chronic pancreatitis. Previous studies investigated COX-2 as a therapeutic target. These reports showed a reduced pathology in COX-2-deficient mice with a better outcome. Here we compared the role of COX-2 in acute and chronic pancreatic inflammation using the same COX-2−/− mouse model of cerulein-induced pancreatitis. In a setting of acute pancreatitis, juvenile COX-2−/− mice exhibited a reduced histopathological score compared with wild-type littermates; on the contrary, adult mice did not show any difference in the development of the disease. Similarly, in a setting of chronic pancreatitis induced over a period of 4 wk, adult mice of the two strains showed comparable histological score and collagen dep...

Internal pancreatic fistulas (IPF) are an uncommon but well-recognized complication of chronic pancreatitis (CP) that are associated with significant morbidity and mortality. Because of their low incidence, management is still... more

Internal pancreatic fistulas (IPF) are an uncommon but well-recognized complication of chronic pancreatitis (CP) that are associated with significant morbidity and mortality. Because of their low incidence, management is still controversial. The aims of this study are to report the 8-year experience with IPF management in a Brazil University-affiliated hospital and to propose a management algorithm. A centralized diagnostic index was used to retrospectively identify all patients with IPF admitted to a teaching hospital from 1995 to 2003. The patient's medical records were reviewed for clinical features, diagnostic work-up, treatment strategies, response to therapy, and the length of hospital stay. All patients underwent contrast-enhanced computed tomography of the abdomen and endoscopic retrograde cholangiopancreatography, to guide the therapeutic modality to be offered. Conservative therapy included withholding of oral feedings in conjunction with total parenteral nutrition, oc...

δ-Helices are marginally hydrophobic α-helical segments in soluble proteins that exhibit certain sequence characteristics of transmembrane (TM) helices [Cunningham, F., Rath, A., Johnson, R. M. & Deber, C. M. (2009). Distinctions between... more

δ-Helices are marginally hydrophobic α-helical segments in soluble proteins that exhibit certain sequence characteristics of transmembrane (TM) helices [Cunningham, F., Rath, A., Johnson, R. M. & Deber, C. M. (2009). Distinctions between hydrophobic helices in globular proteins and TM segments as factors in protein sorting. J. Biol. Chem., 284, 5395–402]. In order to better understand the difference between δ-helices and TM helices, we have studied the insertion of five TM-like δ-helices into dog pancreas microsomal membranes. Using model constructs in which an isolated δ-helix is engineered into a bona fide membrane protein, we find that, for two δ-helices originating from secreted proteins, at least three single-nucleotide mutations are necessary to obtain efficient membrane insertion, whereas one mutation is sufficient in a δ-helix from the cytosolic protein P450BM-3. We further find that only when the entire upstream region of the mutated δ-helix in the intact cytochrome P450BM-3 is deleted does a small fraction of the truncated protein insert into microsomes. Our results suggest that upstream portions of the polypeptide, as well as embedded charged residues, protect δ-helices in globular proteins from being recognized by the signal recognition particle–Sec61 endoplasmic-reticulum-targeting machinery and that δ-helices in secreted proteins are mutationally more distant from TM helices than δ-helices in cytosolic proteins.► δ-Helices are marginally hydrophobic α-helical segments in soluble proteins that exhibit certain sequence characteristics of TM helices. ► We have studied the membrane integration potential of δ-helices selected from secreted and cytosolic proteins. ► Three mutations can turn δ-helices from secreted proteins into TM helices. ► A single mutation turns a δ-helix from a cytosolic protein into a TM helix. ► Upstream secondary structure protects hydrophobic helices from membrane integration.

Between 1969 and 1987, 68 patients with pancreatic pseudocysts were treated. The median cyst size was 10 cm (range 2–25 cm). Nine patients were managed conservatively with resolution of the pseudocyst occurring in eight patients. These... more

Between 1969 and 1987, 68 patients with pancreatic pseudocysts were treated. The median cyst size was 10 cm (range 2–25 cm). Nine patients were managed conservatively with resolution of the pseudocyst occurring in eight patients. These patients had significantly smaller (median 4 cm) cysts compared with those in both percutaneously and surgically treated patients (P<0·01). In 22 patients the pseudocysts (median 9 cm) were punctured percutaneously under ultrasound guidance and the cyst fluid was aspirated or drained through a catheter. Complete resolution occurred in 13 patients after 1–4 (mean 2·8) punctures per patient, regression occurred in six patients after 1–4 (mean 2·0) puncture procedures per patient and three were unchanged. No complications were noted, except that two patients treated percutaneously required additional surgery. Thirty-seven patients were managed surgically (median cyst size 11 cm) with external drainage (12 patients), cystgast-rostomy (17 patients), cystduodenostomy (three patients) cystjejunostomy (three patients) and pancreatic resection (two patients). Resolution of the cyst was noted in 29 patients, regression in five and three were unchanged. Five patients required additional surgery. Twelve complications were seen in ten patients (27 per cent), most frequently after external drainage. One patient died after surgical treatment. Mean hospital stay was 13 days among patients treated conservatively and 30 days in both percutaneously and surgically treated patients. Aspiration or catheter drainage of pseudocyst fluid guided by ultrasonography seems a safe and effective treatment of pancreatic pseudocysts and should be considered as initial therapy. If surgery is required cystgastrostomy is preferred.

In 1848, Claude Bernard described the lipolytic function of the pancreas. His experimental procedure was original and as he always affirmed, easily replicable. In this study we repeated the original Bernardian experiments for... more

In 1848, Claude Bernard described the lipolytic function of the pancreas. His experimental procedure was original and as he always affirmed, easily replicable. In this study we repeated the original Bernardian experiments for emulsification and saponification of fats, following the original descriptions from his laboratory manuscripts. The results were astonishingly similar to those obtained by Bernard, confirming the validity of his experiments and conclusions, as well as emphasising again his original concepts on the importance of experimental repeatability in scientific medicine. Considering the surgical difficulties we encountered, we must conclude that Claude Bernard required great manual dexterity to obtain these results without the benefit of modern technology and anaesthesia.

Exocrine pancreatic insufficiency has been observed in some diabetics with peripheral neuropathy and diarrhea. Several mechanisms may be responsible for this insufficiency: (1) pancreatic atrophy, (2) disruption of the cholinergic... more

Exocrine pancreatic insufficiency has been observed in some diabetics with peripheral neuropathy and diarrhea. Several mechanisms may be responsible for this insufficiency: (1) pancreatic atrophy, (2) disruption of the cholinergic enteropancreatic reflexes, or (3) elevated serum levels of peptides such as glucagon and pancreatic polypeptide which are known to inhibit pancreatic exocrine secretion. To clarify the mechanism(s) involved in this exocrine pancreatic impairment, we studied 10 diabetics with diarrhea and peripheral neuropathy. Their results were compared to those of eight normal volunteers. Each subject underwent a standardized pancreatic function study which assessed nonstimulated secretion, the response to intrajejunal infusion of a mixture of amino acids, and the output following intravenous administration of secretin and cholecystokinin (CCK). In separate studies, the effect of a background infusion of bethanechol and secretin on the pancreatic response to CCK was assessed in six patients and six normal controls. Compared to normals, all diabetics exhibited a significant reduction in both enzyme and bicarbonate secretion to all stimuli. This reduction was not corrected by administering bethanechol. Plasma glucagon and pancreatic polypeptide levels in diabetics were not significantly higher than those in controls. We conclude that diabetics with diarrhea and peripheral neuropathy exhibit impairment of their exocrine pancreatic secretion and possible mechanisms for this are discussed.

The metabolic and hormonal changes during a standard physical exercise were studied in healthy subjects and in insulin-dependent diabetics well matched for body weight, and therefore submitted to a similar work load in a physiologic... more

The metabolic and hormonal changes during a standard physical exercise were studied in healthy subjects and in insulin-dependent diabetics well matched for body weight, and therefore submitted to a similar work load in a physiologic range, and in obese subjects that, owing to their weight, faced a significant heavier work in the same environmental conditions. Moderate work load did not lead to significant changes in metabolic and hormonal blood parameters (blood glucose, FFA and glycerol; insulin, glucagon, growth hormone and cortisol) in healthy subjects. A similar substrate homeostasis was seen in insulin-dependent diabetics, that however showed marked hormonal alterations. In these subjects, indeed, higher levels of plasma glucagon and GH were reached during work and in the recovery phase. Obese subjects, submitted to a heavier work load, presented a marked increase in blood glucose and glycerol which agrees with high GH and cortisol levels, and a subsequent increment of IRI which corresponds to a normalization of blood glucose and glycerol. Obese subjects, therefore, show a normal sensitivity to work load. Considerations about the work load in everyday life are discussed.

Background: The antioxidant defense in the pancreas is low because they are exposed to toxic substances daily. This study aimed to evaluate the ameliorating effect of Viola odorata flowers Extract (VOE) on the pancreas histology and... more

Background: The antioxidant defense in the pancreas is low because they are exposed to toxic substances daily. This study aimed to evaluate the ameliorating effect of Viola odorata flowers Extract (VOE) on the pancreas histology and function in Streptozotocin (STZ)-induced diabetic rats. Methods: Forty male rats were divided into five groups, consisting of controls; STZ; and STZ plus various doses of VOE (100, 200 or 400 mg/kg). The amylase, lipase, insulin and total antioxidant capacity levels were measured in the sera. The homeostatic model assessment of insulin resistance was also measured. The histopathological alterations of the rats' pancreases were examined microscopically. Results: The serum amylase and total antioxidant activities were reduced in diabetic rats (P=0.001). Varying doses of VOE reduced the serum amylase and glucose levels, and increased the total antioxidant activities compared to that of the diabetic rats (P<0.05). There were no significant differences in the serum lipase and insulin levels among the groups. Treatment with VOE at all doses significantly lowered the insulin resistance compared to that of the diabetic group (P=0.001). Significant reductions were observed in the areas of the pancreatic Langerhans islets and the number of beta cells in the STZ group (P=0.001). Conclusion: This study demonstrated that VOE ameliorated the adverse effects induced by STZ in the rat's pancreas in the short-term. These effects are likely to be due to the reduced insulin resistance and amylase activity, and increased total antioxidant activity along with the histopathological alterations in the pancreas.

Metabolic effects of the glucagon-like peptide-1 analog liraglutide and the dipeptidyl peptidase-IV inhibitor vildagliptin were compared in rats made obese by supplementary candy feeding. Female Sprague-Dawley rats were randomized to... more

Metabolic effects of the glucagon-like peptide-1 analog liraglutide and the dipeptidyl peptidase-IV inhibitor vildagliptin were compared in rats made obese by supplementary candy feeding. Female Sprague-Dawley rats were randomized to 12-week diets of chow or ...

For mass spectrometry-based proteomic analyses, electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) are the commonly used ionization techniques. To investigate the influence of the ion source on peptide... more

For mass spectrometry-based proteomic analyses, electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) are the commonly used ionization techniques. To investigate the influence of the ion source on peptide detection in large-scale proteomics, an optimized GeLC/MS workflow was developed and applied either with ESI/MS or with MALDI/MS for the proteomic analysis of different human cell lines of pancreatic origin. Statistical analysis of the resulting data set with more than 72 000 peptides emphasized the complementary character of the two methods, as the percentage of peptides identified with both approaches was as low as 39%. Significant differences between the resulting peptide sets were observed with respect to amino acid composition, charge-related parameters, hydrophobicity, and modifications of the detected peptides and could be linked to factors governing the respective ion yields in ESI and MALDI.