The guppy is a tropical fish that has been used as an experimental model organism in science. It is a species well adapted to the natural environment and that can support adverse environmental conditions, and so, at occasions, its presence can be indicative of environmental disturbances. Moreover, as the liver is very important when studying fish diseases, the knowledge of normal microanatomy is essential to assess histological changes, e.g., related to environmental change or toxic pollutants. The target organ of this histological study is the liver. The main objective is to contribute to the identification of anatomical and structural variations of this organ in different teleost species. We studied the distribution and spatial organization of the different types of blood vessels and biliary ducts and the relationships between them are established. For this, each liver was totally sectioned and the serial sections inspected in detail. The guppy liver presented intra-hepatic pancreatic tissue and so reported its association with the vascular and biliary elements. We observed that the input of afferent vessels (i.e., bringing blood into the liver) occur not only in the hilum but pierce and enter the organ at various points. Within the liver, venous vessels and bile ducts are seen, isolated or associated as venous-arteriolar tracts (VAT), and venous-biliary- arteriolar tracts (VBAT). Sometimes, pancreocytes appear within the liver surrounding isolated veins, forming venous tract with pancreatic acini (VT-P), or dual associations with afferent vessels, forming venous-arteriolar tracts with pancreatic acini (VAT-P). Intrahepatic pancreatic ducts were tiny and rare, putting in question the functional role of the acini. Contrary to other fish species, we did not spot isolated arterioles and associations between these and biliary ducts (BAT).We found aggregates of macrophages, namely associated with afferent and efferent (i.e., draining blood out) venous vessels; the latter fact not commonly reported in other fish species. There was a reduced arterialization of the organ (as arterioles were extremely rare), contrasting with an over predominance of a random distribution of the venous vascularization. The guppy differs to some extent from other previously studied models, highlighting the importance of making this kind of study to offer specific frameworks that can explain specific physiological processes or avoid misinterpretations; for instance about gene expression, as the whole liver specific expression will reflect the presence of hepatocytes and pancreocytes as well.Copyright © 2017 Elsevier Ltd. All rights reserved.

The fine structures, enzyme histochemical, and immunohistochemical characterization of liver in zebrafish were investigated using light microscopy and electron microscopy. The results showed that liver was separated into three lobes and each lobe had a central vessel comparable to the mammalian central vein. However typical hepatic lobules, portal areas, and hepatic arteries were not observed. A portal vein entered the liver and its tributaries were connected directly to the sinusoids, which then converged to the central vessel. Three central vessels in lobes finally carried the blood out of liver. The polygonal and bilayered hepatocytes were arranged as twisting, branching, and anastomosing cords. Ultrastructurally, they showed apparent morphological features of protein synthesis and secretion. Bile entered the biliary tree through the intracellular canaliculus, the ramifications of intercellular canaliculi that originated near the hepatic nucleus and then extended to the hepatocyte surface where two adjacent hepatocyte membranes formed intercellular canaliculi, and then ran sequentially through bile preductules, bile ductules, and bile ducts to be secreted out of the liver. Bile preductular epithelial cells (BPs) were cells located between bilayered hepatocytes in one hepatic cord. Occasionally, some tight junctions were detected forming the link between BPs and hepatocytes, which led us to assume that BPs might have a close relationship with hepatocytes during evolution. The present results indicate that zebrafish liver has its own specific fine structure.Copyright © 2012 Wiley Periodicals, Inc.

Human proliferating cell nuclear antigen (hPCNA) containing a single amino acid substitution at position 85, that of lysine for glutamate (E85K), was compared to wild-type (wt) hPCNA for its ability to promote DNA synthesis by purified DNA polymerase delta (pol delta) both on unmodified templates and past chemically defined template base lesions (translesion synthesis; TLS). Significant enhancement (up to 4-5-fold or greater) was seen but depended both on the exact PCNA/pol delta ratio tested and on the specific nature of the template (e.g., unmodified versus lesion-containing; chemical nature of the template base lesion). These results suggest that human PCNA, either mutated to contain lysine (K) at position 85 or bearing similar primary mutations, would promote more secondary mutagenesis in cells and/or tissues where PCNA is normally expressed at low levels relative to pol delta. Over an entire lifetime, such secondary mutagenesis could be biomedically significant.

Proliferating cell nuclear antigen (PCNA) is a DNA sliding clamp interacting with multiple partners in DNA transactions such as DNA replication/repair and recombination as well as chromatin assembly. We previously detected and purified by chromatographic procedures a 31 kDa PCNA from cultured wheat cells (Triticum monococcum L). Here we report the complete sequence of the wheat 31 kDa PCNA showing a very high aminoacid identity with its plant counterparts (maize and rice). This recombinant PCNA has been used as a bait in an affinity chromatography procedure, in order to capture PCNA interacting proteins. We detected by liquid chromatography, tandem mass spectrometry and search in plant protein databases, several specific bands from wheat cell lysates in fractions bound to wheat PCNA-affinity column. One of them is the wheat elongation factor 1A. Its putative regulatory role in DNA replication/repair is discussed.