1,720,957 research outputs found
Association between islets of Langerhans and pancreatic ductal system in adult rat. Where endocrine and exocrine meet together?
No full textStudies 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
Glial Fibrillary Acidic protein (GFAP)-like immunoreactivity in rat endocrine pancreas
No full textThe study of intermediate filament expression in the pancreatic epithelium has been previously focused almost exclusively on cytokeratins. A transient vimentin-immunoreactivity has also been detected within ductal cells in rat foetal pancreas. Here, we report that in rat pancreas an intense GFAP-like immunoreactivity is detectable within a sub-population of endocrine cells located in the periphery of the islet of Langerhans. In addition, staining appeared to be prevalently located in the apical pole of the cells. Two different polyclonal antibodies have been employed in the present study with analogous results. Staining of consecutive sections with anti-GFAP, anti-glucagon and anti-somatostatin antibodies demonstrates that GFAP-like immunoreactivity is present within glucagon-secreting cells. The relevance of this finding is discussed
The peculiar pattern of type IV collagen deposition in epiretinal membranes
No full textIdiopathic 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 labelled for type IV collagen suggesting an active role in membrane remodelling. 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
Pancreatic lymphatic system in rodents
No full textThe 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
The arterial blood supply of the pancreas : a review IV. the anterior inferior and posterior pancreaticoduodenal aa., and minor sources of blood supply for the head of the pancreas
No full textThe 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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
