From chronic overfeeding to hepatic injury: role of endoplasmic reticulum stress and inflammation.

We analyse how chronic overfeeding, by increasing circulating fatty acids, might lead to inflammation, insulin resistance (IR) and injury in the liver. Chronic overfeeding causes an increase in adipose tissue depots and is characterised by an increased presence of hypertrophic adipocytes when adipose tissue expandability is inadequate. Adipocyte hypertrophy is a possible stress condition for the endoplasmic reticulum (ER), which will activate inflammatory and apoptotic pathways and cause IR in adipose tissue. Insulin-resistant adipocytes, being more lipolytic and less liposynthetic, induce an increase in circulating free fatty acids. Moreover, the strongly compromised secretion/function of the adipocyte hormones, adiponectin and leptin, decreases lipid oxidation, particularly in the liver, causing lipid accumulation, ER stress and IR in hepatocytes. ER stress may lead to reduced very-low-density lipoprotein (VLDL) secretion and increased lipogenic gene expression despite the presence of IR. These events and reduced lipid oxidation may lead to further hepatic lipid accumulation. When the triglyceride storage capacity of hepatocytes is exceeded, hepatic injury may occur. ER-stressed steatotic hepatocytes activate apoptotic and inflammatory pathways, which trigger IR and the release of chemokines and cytokines, and these, in turn, elicit an increased influx of Kupffer cells (KCs) and hepatic stellate cells (HSCs) around dying hepatocytes. Soluble mediators, secreted mainly by ER-stressed steatotic hepatocytes and activated KCs, induce the transdifferentiation of HSCs to myofibroblasts, which secrete fibrogenic cytokines and matrix components that trigger fibrosis. In conclusion, chronic lipid overloading due to inadequate fat-storing capacity of adipose tissue can induce hepatic injury when triglyceride storage capacity of hepatocytes is exceeded.

PPARalpha mediates the effects of the pesticide methyl thiophanate on liver of the lizard Podarcis sicula.

The majority of environmental pollutants are potential peroxisomal proliferators which include a heterogeneous group of compounds known to determine massive peroxisomal proliferation and hepatocarcinogenesis in rodents. Peroxisomal proliferation is accompanied by the induction of the peroxisomal fatty acid beta-oxidation pathway mediated by a class of transcription factors named peroxisome proliferators activated receptors (PPARs). This phenomenon demonstrated also in ectotherm animals after exposition to environmental pollutants may be utilized as biomarker in environmental impact studies. In the present work we have tested the sensitivity to methyl thiophanate (TM) of the lizard Podarcis sicula in order to propose a biological model for monitoring the ecotoxicological effects of this pesticide on terrestrial sentinel species. The data obtained demonstrate that exposition to sub-lethal concentrations of TM leads to hepatocellular morphological changes and glycogen depletion, apoptosis, as well as probable peroxisomal proliferation attested by the increase of acyl-CoA oxidase (AOX). This effect seems to be mediated by the concomitant increase of PPARalpha. On the basis of these results we propose that also in Podarcis sicula, as just proposed for aquatic organisms, peroxisomal proliferation and AOX increase may be considered new biomarkers to evaluate pollution by organic compound in terrestrial environments.

Morphology of the pancreas of some species belonging to the genera Phelsuma and Gecko (family Gekkonidae): evidence of apoptotic process during the seasonal cycle.

In this study we investigated comparative morphology of the endocrine pancreas of several species belonging to the family Gekkonidae and apoptotic processes of the pancreas which may be correlated to the seasonal cycle. The following species of the family Gekkonidae were studied: Phelsuma lineata, P. madagascariensis, P. dubia, P. abotti, Gekko gecko, G. vittatus, and Geckonia chazaliae. In all these species the pancreas consisted of large and medium islets as well as endocrine cells which were scattered throughout the acinar cells. Exocrine parenchyma consisted of tubuli-acini. Four mayor cell types were identified in the endocrine pancreas, using immunocytochemistry: glucagon-immunoreactive (A) cells, insulin-immunoreactive (B) cells, somatostatin-immunoreactive (D) cells, and pancreatic polypeptide immunoreactive (PP) cells. In the endocrine pancreas the amount of A cells and B cells was either equal or a prevalence of A cells was observed. In the wet season the pancreatic morphology presented normal features with very rare apoptotic cells. The animals belonging to the genus Phelsuma taken in the dry season (July) showed numerous vacuolated, Caspase 3, 9 and 11-immunoreactive acinar and some endocrine cells containing picnotic nuclei which were positive to tunel reaction. The animals belonging to the genus Gekko taken at the end of the dry season (October) exhibited strongly vacuolated, Caspase 3, 9 and 11-immunoreactive endocrine and some acinar cells containing nuclei which were positive to tunel reaction. These apoptosis events could be a reaction in response to stress mechanisms, such as a starvation period during the dry season.

Leptin, leptin receptors and ACTH immunoreactivities are present in the gastrointestinal tract and the neural tube of tadpoles of the newt Triturus.

Leptin, its receptor and ACTH were detected by immunohistochemistry in the gastrointestinal tract and the neural tube of the amphibian urodele, Triturus cristatus carnifex, during development. These molecules were found after hatching of tadpoles, starting from stage 41. In the gastrointestinal tract, cells immunoreactive to leptin and its receptor were first revealed in the stomach, the liver and the gut and then in the pancreas. Both immunoreactives were colocalized in the same cells in some areas. Immunostaining for ACTH appeared at stages 43/45 in the stomach, the gut and the pancreas. In adjacent sections, a few cells immunoreactive to both ACTH and leptin receptor were detected. A few cells were immunoreactive to both insulin and leptin receptor. Immunoreactivities to leptin and its receptor were also found in adjacent sections of the neural tube, often colocalized in the same cell. Moreover, in prosencephalon, mesencephalon, rhomboencephalon and spinal cord, ACTH-immunoreactive cells were detected in the same areas as the leptin receptor immunoreactive cells. These results suggest the existence of a neuroendocrine network in newt tadpoles both at the central level, where it resembles that of mammals, and at the peripheral level, where it may act locally to regulate food intake and metabolism, e.g. yolk digestion.

An immunocytochemical study of intrapancreatic ganglia, nerve fibres and neuroglandular junctions in Brockmann bodies of the tompot blenny (Blennius gattoruggine), a marine teleost.

The innervation of the Brockmann bodies in the teleost fish, Blennius gattoruggine, was studied using immunocytochemical techniques at both the light and electron microscopy levels. Islet innervation consisted of intrapancreatic ganglia, generally localized inside the rim of the exocrine tissue of the Brockmann bodies, in proximity to the islet, nerve fibres and nerve terminals with synaptic complexes. The intrapancreatic ganglia were of variable size, with different numbers of ganglionic cells, that appeared unipolar in section. The cell bodies showed immunoreactivity to galanin, oxytocin, peptide tyrosine tyrosine and glucagon. The extrinsic and intrinsic nerve fibres passed through the exocrine parenchyma and crossed the connectival septa and islet connectival sheath, penetrating into the islets, where they became increasingly thinner. They terminated on the endocrine cells with dilated nerve terminals. At least three types of terminals were detected, depending on the different vesicle content: peptidergic, cholinergic or adrenergic. They presented specialized synaptic structures, the neuroglandular junctions, some of which contained neurosecretory granules immunogold labelled by galanin antiserum. This new finding confirms the role of galanin as a neurotransmitter. This rich supply of innervation may be important in the regulation and integration of islet secretion.

PP/PYY cells from endocrine pancreas of the scincid lizard Eumeces inexpectatus synthesize ACTH- and alpha-MSH-like molecules.

The endocrine pancreas of the scincid lizard Eumeces inexpectatus secretes four major hormones, insulin, glucagon, somatostatin, and pancreatic polypeptide (PP); in addition, other peptides and neuropeptides, often colocalized in one of the principal cell types (A, B, D, and PP), were detected by light and ultrastructural immunocytochemistry. In particular, the pancreas is rich in peptide tyrosine tyrosine (PYY), ACTH, and alpha-MSH immunoreactivity. When single- and double-immunolabeled serial sections were compared for immunostaining for PP, PYY, ACTH, and alpha-MSH, there was broad coincidence with PP, termed PP/PYY, cells in view of the extensive colocalization of these two peptides. Furthermore, ultrastructural morphometric studies revealed similar secretory granules for PP immunoreactive (ir) and ACTH ir cells, while the endocrine cells express pro-opiomelanocortin (POMC) mRNA, indicating an active, extrapituitary synthesis of the POMC-derived peptides in these cells. In conclusion, the presence of POMC-derived peptides in the endocrine pancreatic cells suggests that they may regulate insulin secretion.

Morphological basis of the interactions between endocrine cell types in the pancreatic islets of the teleost, Blennius gattoruggine.

The endocrine pancreas of the teleost fish Blennius gattoruggine was studied by immunochemistry using both light and electron microscopy. Generally, one large Brockmann body, along with intermediate and small islets, was found. Cells immunoreactive (IR) to anti-insulin (B), anti-glucagon (A) anti-somatostatin (D) anti-pancreatic polypeptide and anti-PYY sera were detected with B cells located at the center of the islet and the other cell types forming a peripheral mantle. The B-cell cytoplasm showed rows of microtubules close to the secretory granules and perpendicular to the plasmalemma. The ultrathin section images revealed exocytotic and endocytotic features, and the presence of intercellular gap junctions between the plasmalemma of contiguous cells, suggesting intercellular routes of communication, e.g. via autocrine and/or paracrine mechanism. These features were observed in all of the cell types, and were abundant in D cells. D cells were particularly numerous in the islets and were disposed close to A and B cells, as observed in other teleost species. The most peripheral B cells, in closer contact with D cells than the central ones, appeared strongly immunolabeled, perhaps owing to the inhibitory action of somatostatin. Some D cells exhibited a long protrusion directed towards the center of the islet. In view of their cytological characteristics and their secretion, D cells might have an important role in the modulation of A and B-cell secretion in an endocrine and/or paracrine fashion.

Islets and diffuse endocrine component in the pancreas of three red frogs species: relationships between endocrine and exocrine tissue.

The endocrine pancreas of three red frogs was studied immunohistochemically. It consisted of islets and diffuse endocrine cells. The islets showed a mammalian-like arrangement with a central core of B cells and a peripheral mantle of A/PP cells. A few D and VIP cells were also present. Several regulatory peptides were co-localized in the same endocrine cells by consecutive sections and double-labeling studies. The A/PP cells were formed by subpopulations of cells showing various types of immunoreactivity and varying degrees of immunolabeling. Generally, glucagon/pancreatic polypeptide, glucagon/pancreatic polypeptide/peptide tyrosine tyrosine and glucagon/pancreatic polypeptide/neuropeptide tyrosine immunoreactivities were present in the islets and in the endocrine cells scattered throughout the exocrine parenchyma (the diffuse component). Some specimens, mainly belonging to Rana dalmatina, showed evident periinsular halos around the islets. The diffuse component was abundant, and mainly contained A/PP cells. It formed a net across the exocrine parenchyma; its interrelationship with the latter might occur by a paracrine mechanism.

PeptideYY and insulin coexist in beta-granules in B cells of the Madagascan lizard, Zonosaurus laticaudatus.

PYY, a 36-amino-acid peptide belonging to the PP family, is often colocalized with glucagon in A cells in the gastroenteropancreatic system of vertebrates. However, both immunocytochemical and immunohistochemical methods reveal this peptide in insulin-containing beta-granules in the lizard Zonosaurus laticaudatus. Absorption tests of PYY antiserum with insulin did not abolish the immunostaining of beta-granules with PYY antiserum, ruling out a cross-reaction between the PYY antiserum and insulin. This feature may be a reflection of the persistence of an ontogenetic character or a result of an adaptative mechanism that selectively activates the PP family of genes in the cellular line of B rather than of A cells.

Immunocytochemical detection of islet hormones in the digestive system of Protopterus annectens.

The presence, distribution, and interrelationships of the four typical pancreatic islet hormones were investigated in the digestive system of Protopterus annectens by single and double immunohistochemical methods. Insulin-, glucagon-, and somatostatin-immunoreactive (IR) elements were detected in both the pancreas and the gut. Pancreatic polypeptide (PP)-IR endocrine cells were always present in the gut, but were only present in the pancreas of a few specimens. Some of the latter cells also seemed to react with glucagon antiserum. In the pancreas the immunopositive cells were organized into islets of different sizes, and their organizations were studied by the double immunohistochemical techniques. In the few large islets insulin-IR cells were present in the central zone, glucagon- and PP-IR cells at the periphery, and somatostatin-IR cells intermingled with both the peripheral and the central endocrine cells. In the smaller islets, the number and the staining intensity of glucagon- and PP-IR endocrine cells varied markedly. In the gut, insulin-, somatostatin-, and PP-IR cells were of the open type; glucagon-containing cells were very few and had no luminal contact. They were differently distributed along the intestinal epithelium. Somatostatin-IR nerve fibers and somatostatin-IR neuron cell bodies were also observed in the intestinal wall. The organization of pancreatic endocrine cells in P. annectens is similar to that observed in the majority of teleosts even if a different topographical association can be found. Furthermore, islets of different sizes seem to display a different metabolic turnover, and the detection of pancreatic PP-immunoreactivity varied according to the specimens utilized. In the intestinal portion insulin-IR cells, in addition to PP-, glucagon- and somatostatin-IR cells are present: this suggests that intestinal insulin-like immunoreactivity may be more widespread than previously supposed.

The endocrine pancreas of lacertids: an immunocytochemical study of the genera Pedioplanis and Meroles.

The endocrine pancreas from 2 genera of lacertid lizards (Pedioplanis and Meroles) was investigated immunocytochemically for the presence of immunoreactivity to mammalian antisera to insulin (I), glucagon (G), pancreatic polypeptide (PP), peptide tyrosine tyrosine (PYY), neuropeptide tyrosine (NPY), somatostatin 14 (SRIF 14) and somatostatin 28 (SRIF 28), pancreastatin (Pst), galanin (Gl), oxytocin (OT). Cells immunoreactive (IR) to all the antisera used, and nerve fibers IR only to anti-galanin were found. Moreover, three types of colocalized immunoreactivities were detected: type 1 (PP/PYY/NPY), type 2 (G/PP/PYY/NPY), and type 3 (G/PYY/NPY/Pst).

Cell composition and co-stored peptides in the endocrine pancreas of Rana arvalis.

The endocrine pancreas of Rana arvalis studied by immunochemistry consisted of islets and diffuse endocrine cells. The islets showed a mammalian-like arrangement with a central core of B cells and a peripheral mantle of A/PP cells. A few D and vasoactive intestinal polypeptide cells were also present. Consecutive sections or double-labeling studies allowed us to detect several regulatory peptides colocalized in the same endocrine cells. The so-called A/PP cells contained subpopulations of cells showing various types of immunoreactivity and varying degrees of immunolabeling. Generally, glucagon/pancreatic polypeptide, glucagon/pancreatic polypeptide/phe-met-arg-phe-amide, glucagon/pancreatic polypeptide/peptide tyrosine tyrosine, glucagon/pancreatic polypeptide/peptide tyrosine tyrosine/phe-met-arg-phe-amide immunoreactivities were present in the islets, while peptide tyrosine tyrosine/neuropeptide tyrosine colocalization was also found in the parenchyma.

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

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

Endocrinologic effects of the anaesthetic propofol.

Because of the similarities of the adrenal glands of mammals and of the lizard Podarcis s. sicula, the latter has already been the subject of various studies on the effects of Propofol and other anaesthetics. Because a relationship between the activities of the thyroid and adrenal glands of this species has been demonstrated, the authors administered Propofol to a species of lizard to investigate its effects on the thyroid gland. Propofol inhibited thyroid activity, promoted steroid synthesis, and caused the contemporaneous appearance of both adrenaline and noradrenaline granules in the cytoplasm of the chromaffin cells. These results suggest that inhibition of the activity of the thyroid gland is secondary to the action of Propofol on the adrenal gland.

The endocrine pancreas of Podarcis s. sicula Raf.: an immunocytochemical study at light and electron microscopic levels.

The endocrine pancreas of Podarcis s. sicula Raf. was investigated at light and electron microscopic levels using immunocytochemical methods. It was constituted by endocrine islets, which were concentrated more in the splenic than in the duodenal region, and never formed large clusters. At the light and electron microscope, with the peroxidase-antiperoxidase reaction (PAP) and the colloidal gold technique, four cell types were identified: glucagon-positive A-cells, insulin-positive B-cells, somatostatin-positive D-cells and pancreatic polypeptide-positive F- or PP-cells. F- or PP-cells showed a different regional distribution, being absent or very rare in the splenic lobe of the pancreas and numerous in the duodenal lobe, where they were seldom found in the islets, but were scattered in the exocrine parenchyma. The functional meaning of F-cells is discussed. The E.M. observations were carried out at the CIRUB (Centro Interdipartimentale di Ricerca sulle Ultrastrutture Biologiche) of the University of Naples.

The endocrine pancreas of Triturus cristatus: an immunocytochemical study.

The endocrine pancreas of Triturus cristatus carnifex was studied with the aid of immunocytochemical methods, showing cells immunoreactive to anti-insulin serum (B cells), a small population of cells immunoreactive to anti-glucagon serum only (A cells), rare cells positive to anti-PP serum only (PP or F cells), and a larger population of cells immunoreactive both to anti-glucagon and to anti-PP sera. B cells lied in the core of the islet, while the A/PP cells were located at the periphery, forming digitations extending into the exocrine parenchyma. D cells were present in small number in the islet while they were more numerous scattered in the exocrine parenchyma. A/PP cells as well as D cells showed one or two long cytoplasmic extensions often in contact with blood vessels.

[Angiodysplasia of the colon]. / L'angiodisplasia del colon.

The Authors report their experience with a case of angiodysplasia of the colon. It is outlined how these lesions can be demonstrated by angiography and colonoscopy. The pathophysiology, diagnosis and management are discussed as well.