The present article is the fourth part of a comprehensive review of the arterial blood supply of the pancreas and completes the study of the arterial vascularization of the pancreatic head dealing with the anterior inferior and posterior inferior pancreaticoduodenal aa. and with some minor sources of blood supply not involving the classical system of the pancreaticoduodenal arches. The aim of this review is to summarise the anatomical studies, starting from Haller's reports, and to supply, as far as possible with original material, angiographic evidence for the classic anatomical concepts. For this purpose, 1015 selective angiographs (celiac trunk and its branches, superior mesenteric a.) were taken from the angiographic archives of the Institutes of Radiology of Siena, Rome (Catholic University), and Perugia. These demonstrated the anterior inferior pancreaticoduodenal a., present in most instances, as arising from the inferior pancreaticoduodenal a., from a common trunk with the posterior inferior pancreaticoduodenal a. and the 1st jejunal a., from the 1st jejunal a. or from the superior mesenteric a.; on the other hand, the posterior inferior pancreaticoduodenal a. was more variable, originating from the inferior pancreaticoduodenal a., from a common trunk with the anterior inferior pancreaticoduodenal a. and the 1st jejunal a., from the superior mesenteric a., from the dorsal pancreatic a., or from a right accessory hepatic a. coming from the superior mesenteric a. In addition, minor branches to the head of the pancreas arose from the gastroduodenal a., the dorsal pancreatic a., the common hepatic a. and the inferior right phrenic a. Other origins of the inferior pancreaticoduodenal aa. previously reported, but not angiographically detectable with certainty, as well as further minor sources of blood supply to the head of the pancreas, have been listed. The differing opinions regarding the incidence of the various ways the inferior pancreaticoduodenal aa. arise are discussed and an attempt is made to explain the variability of the vascular anatomy of the pancreatic head on embryologic grounds.

It is common to describe the endocrine and the exocrine pancreas as if they were two distinct and independent entities. However the pancreas is an integrated organ involved in the digestion and absorption of nutrients on the one hand, and in the regulation of blood glucose homeostasis, on the other. Most probably, the unique anatomical architecture of this organ, characterized by the dispersion of the endocrine component throughout the acinar parenchyma as hundreds of thousands variable-sized clusters of endocrine cells (islets of Langerhans), has evolved to facilitate interactions between the two glandular components [1]. In order to determine reciprocal influences, many aspects of the relations occurring between exocrine and endocrine pancreas have been investigated in the past three decades [2,3]. Because of the observation that, in contrast to ªtele-insularº acini, ªperi-insularº acini are formed by larger cells, containing more zymogen granules [2, 4±6], numerous studies have addressed the role(s) played by the islet hormones in tuning acinar cell secretion and the anatomical pathways, the so called ªislet-acinar axisª, through which this influence is exerted [2,3,7]. A large body of evidence indicates that a continuous insulo-acinar venous portal system conveys hormone enriched blood from the islets to the acinar parenchyma [2, 3, 8, 9]. The amount of acinar tissue that is ac- Diabetologia (2001) 44: 575±584 Association between islets of Langerhans and pancreatic ductal system in adult rat. Where endocrine and exocrine meet together? AbstractAims/hypothesis. Studies on the functional and morphological relations between exocrine and endocrine pancreas have been conducted mainly to disclose the influence of islets of Langerhans on acinar parenchyma. Less attention has been paid to the relations occurring between islets and pancreatic ducts. Methods. A series of consecutive sections of normal adult rat pancreas were double stained with islet (hormones) and duct (cytokeratin 20) markers. Electron microscopy was conducted to investigate the ultrastructural features of duct-islet relations and anti-insulin immunogold labelling was carried out to reveal the presence of insulin in the pancreatic duct system. Results. Consecutive double-stained sections demonstrated that 73.60 2.97 % of the islets were attached to the ducts. For each series, 93.48 5.43 % of the islets contacting the duct tree were associated with small-sized ducts or centroacinar cells. Electron microscopy revealed that some insulin and somatostatin cells do face the duct lumen. Insulin was detected within the duct lumen and in the endosomal compartment of the duct cells. Conclusions/interpretation. The finding that most islets are connected with the duct system in the adult pancreas is discussed in terms of hormone secretion into the ducts, islet histogenesis and the relation among the three tissue components of the pancreas, the endocrine, the exocrine and the duct system. [Diabetologia (2001) 44: 575±584]

Idiopathic epiretinal membranes are sheets of tissue that develop in the vitreoretinal interface. They are formed by cells and extracellular matrix, and they are considered the expression of a fibrotic disorder of the eye. Confocal and immunoelectron microscopy of the extracellular matrix of excised membranes, revealed high contents of type IV collagen. It was distributed within epiretinal membranes in basement membrane-like structures associated with cells and in interstitial deposits. In both cases, type IV collagen was always associated with type I collagen. Col IV was also coupled with Col VI and laminin. At high magnification, type IV collagen immunolabelling was associated with interstitial deposits and showed a reticular appearance due to the intersection of beaded microfilaments. The microfilaments are about 12 nm in diameter with interbead distance of 30–40 nm. Cells of the epiretinal membranes showed intracellular lysosome-like bodies heavily labeled for type IV collagen suggesting an active role in membrane remodeling. Hence, type IV collagen is not necessarily always associated with basement membranes; the molecular interactions that it may develop when not incorporated in basement membranes are still unknown. It is conceivable, however, that they might have implications in the progression of epiretinal membranes and other fibrotic disorders.

The lymphatic network of the pancreas has been little investigated and recent studies have provided contrasting data. This research is aimed to supply the morphologic basis to outline the involvement of the lymphatic system in pancreatic pathology. Guinea pigs, rats, and mice were anesthetized with ether and sacrificed with the same anesthetic. Pieces of pancreas were processed for transmission electron microscopy. Semithin sections were observed by light microscopy and, after positive identification by transmission electron microscopy, lymphatics were followed with long series of consecutive sections to define their distribution. Lymphatics were detected in the pancreas of all the animals both in the inter and the intralobular sites. Closer relations with the exocrine parenchyma (ducts and acini) were observed in guinea pig pancreas. Remarkably, interesting relationships between lymphatics and endocrine tissue were observed in all the animals. Overall, however, the lymphatic network of rat pancreas was less develop and preferentially associated with blood vessels. The distribution of the pancreatic lymphatic network appears consistent with an active role in pancreatic pathology. Anat Rec 263: [155][156][157][158][159][160] 2001.

SUMMARYThe study of intermediate filament expression in the pancreatic epithelium has been previously focused almost exclusively on cytokeratins. Transient vimentin immunoreactivity has also been detected in duct cells of rat fetal pancreas. Here we report that, in rat pancreas, intense GFAP-like immunoreactivity is detectable in a subpopulation of endocrine cells located in the periphery of the islet of Langerhans. In addition, staining appeared to be preferentially localized to the apical pole of the cells. Two different polyclonal antibodies were employed in this study, with analogous results. Staining of consecutive sections with anti-GFAP, anti-glucagon, and anti-somatostatin antibodies demonstrates that GFAP-like immunoreactivity is present in glucagon-secreting cells. The relevance of this finding is discussed.