Osmium tetroxide post-fixation and periodic acid-Schiff dual-staining technique to demonstrate intracellular lipid and glycogen in the mouse liver section – a novel method for co-visualization of intracellular contents in paraffin-embedded tissue

Morphological features of hepatic lipid changes in bearded dragons (Pogona vitticeps), and a proposed grading system

Hepatic lipidosis is commonly diagnosed in pet bearded dragons (Pogona vitticeps). However, there are no studies detailing the histological features of hepatic lipid changes in this species. This study describes the microscopic features of lipid change and details an associated scoring system. Histologic hepatic sections were retrospectively evaluated from 252 bearded dragons submitted for necropsy. Pathologic assessment was used to develop a grading scheme with 2 qualitative, 1 quantitative, and 6 semi-quantitative microscopic parameters, which were refined based on variability. The final grading system developed for diffuse and panlobular lipid accumulation included 2 semi-quantitative and 1 quantitative categories: percentage of hepatocellular vacuolation, fibrosis, and hepatocellular swelling, respectively. Hepatocellular swelling was indirectly quantified by counting the number of nuclei per unit area. There was a strong positive correlation (P < .001) between the percentage of hepatocellular vacuolation and lipid content, a strong negative correlation (P < .001) between nuclear count and lipid content, and a moderate correlation (P < .001) between fibrosis and lipid content. Each category was given a numerical value ranging from 0 to 4, with the sum of each representing the final grade. Cutoff values stratified microscopic changes into mild (final grade 1-4), moderate (5-7), and severe (≥8). There was strong interrater agreement for assessment of vacuolization, fibrosis, and severity classification and moderate for hepatocellular swelling. This study documents the features of hepatic lipid changes in bearded dragons. Although a cutoff to differentiate pathologic from nonpathologic lipid accumulation could not be estimated, the proposed grading scheme can be used to inform future studies.

Fat augments leptin-induced uterine contractions by decreasing JAK2 and BKCa channel expressions in late pregnant rats

Altered lipid metabolism in obesity causes pregnancy complications in humans and animals. Leptin levels increase in pregnancy, as well as obesity. However, the effect of obesity on uterine leptin receptors and its distal signaling is not clear. The present study aimed to understand the effect of increased fat on leptin signaling in rat uterus. Wistar female rats were fed with an HF diet (40% Fat, 17% Sucrose, 1.25% Cholesterol, 0.75% Cholic acid) for 6 weeks before the mating and during pregnancy. HF diet significantly increased the fat depots, liver weight, serum, and tissue cholesterol levels. It produced fatty degeneration in the liver and caused infiltration of inflammatory cells, cystic endometrial glands, and sub endometrial fibrosis of the uterus. In isometric tension experiments, leptin caused a significant increase in uterine contractions in high fat-fed animals compared to control animals. Analysis of receptor expressions revealed no significant difference between the groups. However, a significant decrease in the JAK2 and BKCaα mRNA expression was observed in the uterus of high fat-fed rats. No change in the BKCaβ, eNOS, iNOS, MLCP, and MLCK mRNA expressions was noticed in the HF group compared to the control. The findings of the present study suggest that the contractile response to leptin in the uterus of high fat-fed rats may be attributed to reduced signaling through JAK2 and, lowered expressions of BKCa channel α subunits.

The role of maternal high fat diet on mouse pup metabolic endpoints following perinatal PFAS and PFAS mixture exposure

Per- and polyfluoroalkyl substances (PFAS) are a family of chemicals that are ubiquitous in the environment. Some of these chemicals, such as perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonate (PFHxS) and perfluorooctanoic acid (PFOA), are found in human sera and have been shown to cause liver steatosis and reduce postnatal survival and growth in rodents. The purpose of this work is to evaluate the impact of diet and PFAS exposure to mouse dam (mus musculus) on the risk to pup liver and metabolism endpoints later in life, as well as evaluate PFAS partitioning to pups. Timed-pregnant dams were fed a standard chow diet or 60 % kcal high fat diet (HFD). Dams were administered either vehicle, 1 mg/kg PFOA, 1 mg/kg PFOS, 1 mg/kg PFHxS, or a PFAS mixture (1 mg/kg of each PFOA, PFOS, and PFHxS) daily via oral gavage from gestation day 1 until postnatal day (PND) 20. At PND 21, livers of dams and 2 pups of each sex were evaluated for lipid changes while remaining pups were weaned to the same diet as the dam for an additional 10 weeks. Dam and pup serum at PND 21 and PND 90 were also evaluated for PFAS concentration, alanine aminotransferase (ALT), leptin and adiponectin, and glycosylated hemoglobin A1c. Perinatal exposure to a HFD, as expected, increased pup body weight, maternal liver weight, pup liver triglycerides, pup serum ALT, and pup serum leptin. PFOA and the PFAS mixture increased liver weights, and. treatment with all three compounds increased liver triglycerides. The maternal HFD increased dam and pup serum PFAS levels, however, was protective against PFOA-induced increase in serum ALT and observed increases in liver triglycerides. The PFAS mixture had very distinct effects when compared to single compound treatment, suggesting some cumulative effects, particularly when evaluating PFAS transfer from dam to pup. This data highlights the importance of diet and mixtures when evaluating liver effect of PFAS and PFAS partitioning.

Fish telocytes and their relation to rodlet cells in ruby-red-fin shark (rainbow shark) Epalzeorhynchos frenatum (Teleostei: Cyprinidae)

Telocytes comprise the major constituents of the supportive interstitial framework within the various organs. They form a 3D network between different types of stromal and non-stromal cells, which makes them distinctively vital. We have previously explored the origin of the peculiar rodlet cells, especially on their differential stages in aquatic species. The current study aimed at highlighting the relation of telocytes with different rodlet stages. Samples of fish, olfactory organs, and gills were processed for semi thin sections, transmission electron microscopy, and immunohistochemistry. It was evident in the study that telocytes formed a 3D interstitial network, entrapping stem cells and differentiating rodlet cells, to establish direct contact with stem cells. Differentiated stem cells and rodlet progenitor cells, practically in the granular and transitional stages, also formed ultrastructure junctional modifications, by which nanostructures are formed to establish cell contact with telocytes. Telocytes in turn also connected with macrophage progenitor cells. Telocytes (TCs) expressed CD34, CD117, VEGF, and MMP-9. In conclusion, telocytes established direct contact with the stem and rodlet cells in various differential stages. Telocytes may vitally influence stem/progenitor cell differentiation, regulate rodlet cell function, and express MPP-9 that may regulate immune cells functions especially, including movement and migration ability.

Migratory Activities and Stemness Properties of Rodlet Cells

The current study aimed to characterize different stages of rodlet cells using light microscopy, immunohistochemistry, and transmission electron microscopy. Granular rodlet cells have a distinct granular cytoplasm. Transitional rodlet cells had distinct capsules, and immature granules. Mature rodlet cells were pear-shaped and had elongated granules. Ruptured rodlet cells had a granular cytoplasm. The affinity of rodlet cells for different histochemical techniques was detected. Immunohistochemical analysis of rodlet cells for stem cell markers such as CD117, CD34, proliferation marker, proliferating cell nuclear antigen (PCNA), endopeptidase activity; matrix metalloproteinase-9 (MPP-9) and the angiogenic factor; vascular endothelial growth factor (VEGF) was investigated. All stages of rodlet cells were expressed CD117. However, the ruptured stage was CD117-negative. The granular, transitional, and mature stages had strong CD34 immunoaffinity, while the ruptured rodlet cells were CD34-negative. The most potent immunoreactivity for PCNA was the granular rodlet cells. The transitional cells exhibited less immunoreactivity, while mature rodlet cells had no immunoaffinity for PCNA. All stages of rodlet cells had high enzyme activity as indicated by Acridine orange and exhibited strong MPP-9 immunoaffinity. VEGF is mostly expressed by granular, transitional, and mature rodlet cells. In conclusion, rodlet cells relatively had stemness properties, endopeptidase activity, express a proliferation marker, and angiogenic factors. We suggest a potential role of rodlet cells in immune defense.

Effects of various fixatives and temperature on the quality of glycogen demonstration in the brain and liver tissues

The visualization of glycogen deposits in cells and tissues is important for studying glycogen metabolism as well as diagnosis of glycogen storage diseases. Evidence suggests that the demonstration of glycogen can better be enhanced by factors such the choice of fixative and temperature during fixation. Here, we assessed efficacy of neutral buffered formalin (NBF), alcoholic formalin (AF) and paraformaldehyde (PFA) at 4 °C, 37 °C and 40 °C using Periodic Acid Schiff's staining method. Each liver specimen was fixed in NBF and AF while the brain tissues were fixed in NBF, AF and PFA. We found that there was a better PAS staining intensity with the liver tissues fixed in AF compared with NBF. Also, there was no difference in the quality of the staining for tissues fixed in AF at 37 °C, 4 °C and 40 °C, but fixation with NBF at 4 °C gave the best staining quality when compared with 40 °C and 37 °C. Furthermore, hippocampal tissues fixed in AF showed better quality of PAS staining compared with NBF and PFA. A significant increase in staining intensity was observed for PFA when compared with NBF. Superior staining intensity for PAS was observed at 4 °C for hippocampal tissues fixed with NBF, AF and PFA. Taken together our results show that AF at a temperature of 4 °C gave the best result. Hence, glycogen demonstration can better be enhanced by the choice of fixative and temperature during fixation.

Morphological and immunohistochemical phenotype of TCs in the intestinal bulb of Grass carp and their potential role in intestinal immunity

The current study investigated telocytes (TCs) in the intestinal bulb of Grass carp using light microscopy (LM), Transmission electron microscopy (TEM), scanning electron microscopy, and immunohistochemistry (IHC). By LM, TCs were distinguished by the typical morphological features that had a cell body and telopodes using HE, toluidine blue, methylene blue, Marsland silver stain, Grimelius's silver nitrate, Giemsa, PAS, combined AB pH2,5/PAS, Crossmon's and Mallory triple trichrome, Van Gieson stains, Verhoeff's stain, Sudan black, osmic acid, performic acid with methylene blue and bromophenol blue. TCs were identified under the epithelium as an individual cell or formed a TCs sheath. They detected in the lamina propria, between muscle fibers, around the myenteric plexus and fibrous tissue. TCs acquired immunological features of endocrine cells that exhibited high affinity for silver stain, performic acid with methylene blue, Marsland stain, and immunohistochemical staining using chromogranin A. Sub epithelial TCs were closely related to the endocrine cells. TCs and their secretory activities were recognized using acridine orange. TCs were identified by IHC using CD34, CD117, S100-protein, desmin. TCs formed a3D network that established contact with macrophage, mast cells, dendritic cells, lymphocytes, smooth muscle fibers, fibroblast, Schwann cells and nerve fibers. In conclusion, the localization of TCs in relation to different types of immune cells indicated their potential role in the maintenance of intestinal immunity.