Among the most-used fish species in aquaculture is the Nile tilapia, due to its rapid growth rate and its adaptation to a wide range of farming conditions. A careful description of the morphology of the digestive tract, particularly the esophagus and stomach, allows a better understanding of the relationship between structure and function. Combining scanning and light microscopy we highlighted the presence of five different zones in the stomach (1: esophagus-gastric lumen passage; 2: descending glandular portion; 3: fundic portion; 4: ascending glandular portion; 5: gastric-pyloric transition portion). Histochemical investigation showed a secretion of carboxylates mucopolysaccharides along the esophagus and sulphated complex carbohydrates in the stomach. These results suggest that mucins play a protective role of the epithelial lining, which is essential for a correct digestive process. Finally, the characterization of the main cellular structures may be inspiring for more advanced studies aiming to decipher the role of specific molecules, such as neuropeptides, involved in the physiological digestive process.

NPY is among the most abundant neuropeptides in vertebrate brain and is primarily involved in the regulation of food intake. The NPY system is also associated with the aging process showing beneficial effects on neuronal survival via autophagy modulation. Here, we explore the age-related regulation of NPY in the brain and foregut of the shortest- and longest-lived fish species, Nothobranchius furzeri and Danio rerio, respectively. These two research models, despite some similarities, display profound biological differences making them attractive vertebrates to elucidate the mechanisms underlying the regulation of neuropeptide synthesis and function. It is noteworthy that in both fish species only Npya has been identified, while in the other teleosts two classes of NPY (Npya and Npyb) have been annotated. Our findings document that in both species: (i) NPY is centrally regulated; (ii) NPY levels increase in the brain during aging; (iii) NPY is localized in the enteroendocrine cells as well as in the myenteric plexus and drastically decreases in old animals. According to our data, the age-related regulation in the gut resembles that described in other vertebrate species while the increased levels in the brain offer the unique possibility to explore the role of NPY in model organisms to develop future experimental and translatable approaches.

This study aimed to examine the impact of different surface properties of poly(lactic-co-glycolic) acid (PLGA) nanoparticles (P NPs) and PLGA-Poloxamer nanoparticles (PP NPs) on their in vivo biodistribution. For this purpose, NPs were formulated via nanoprecipitation and loaded with diphenylhexatriene (DPH), a fluorescent dye. The obtained NPs underwent comprehensive characterization, encompassing their morphology, technological attributes, DPH release rate, and thermodynamic properties. The produced NPs were then administered to wild-type mice via intraperitoneal injection, and, at scheduled time intervals, the animals were euthanized. Blood samples, as well as the liver, lungs, and kidneys, were extracted for histological examination and biodistribution analysis. The findings of this investigation revealed that the presence of poloxamers led to smaller NP sizes and induced partial crystallinity in the NPs. The biodistribution and histological results from in vivo experiments evidenced that both, P and PP NPs, exhibited comparable concentrations in the bloodstream, while P NPs could not be detected in the other organs examined. Conversely, PP NPs were primarily sequestered by the lungs and, to a lesser extent, by the kidneys. Future research endeavors will focus on investigating the behavior of drug-loaded NPs in pathological animal models.

First identified as an anorexigenic peptide, in the last decades, several studies have suggested that Nesfatin-1 (Nesf-1) is a pleiotropic hormone implicated in numerous regulatory processes in peripheral organs and tissues. In vertebrates, Nesf-1 is indeed expressed in the central nervous system and peripheral organs. In this study, we characterized the pattern of Nesf-1 distribution within the digestive tract of the common bottlenose dolphin (Tursiops truncatus), composed of three gastric chambers and an intestine without a clear subdivision in the small and large intestine, also lacking a caecum. Our results indicated that Nesf-1 is widely distributed in cells of the mucosal epithelium of the gastric chambers. Most of the immunoreactivity was observed in the second chamber, compared to the first and third chambers. Immunopositivity was also found in nerve fibers and neurons, scattered or/and clustered in ganglion structures along all the examined gastrointestinal tracts. These observations add new data on the highly conserved role of Nesf-1 in the mammalian digestive system.

Background: The setup of experimental protocols able to preserve the anatomical integrity also in terms of organ microarchitecture is mandatory to ensure result translatability. Also, the maintenance of structural integrity perfectly aligns with the refinement implementation aiming to reduce procedure severity, a key issue in animal studies deemed compulsory from both ethical and legal standpoints. Here we report a detailed description of all peri-operative and post-operative care and clinical evaluation in a surgical rat model to test the efficacy of a catheter functionalized by a peptide coating with antimicrobial and antibiofilm properties, whose efficacy was previously tested in vitro. Methods: We used male and female adult Fischer 344 rats (tot n = 44, n = 22 each sex), which were divided into four experimental groups. Each animal underwent refined surgery for the implantation of a functionalized or standard catheter, depending on the group, and was observed for 7 and 14 days. The surgical refinement strategy was based on the placement of the catheter into the bladder lumen rather than in the urethra. Still in the refinement perspective, ultrasound examination of the bladder was conducted to confirm the in situ position of the medical device at an intermediate time point, 4 or 10 days post-surgery depending on the group, while, at the same time, but also at days 0, 7, or 14 post-surgery, an ultrasound-guided cystocentesis was performed to collect sterile urine. The imaging approach was used in place of metabolic cages to minimize distress to the animals and to ensure reliable and unbiased scientific outcomes. Hematological and biochemical parameters were monitored along the preclinical trial; namely, blood sampling was performed at the beginning (day 0) and at the end of the trial (day 7 or 14 post-surgery depending on the group). Results: Clinical scores and biochemical analyses of all animals did not reveal signs of distress or disease. At the endpoints, histological analyses of urinary bladder displayed a well-preserved anatomical structure of the organ without significant signs of inflammatory infiltration into the urothelium. Conclusions: Our model represents a refined strategy to achieve the scientific goals required by the preclinical setting related to catheter-associated urinary tract infections. In particular, it ensures the preservation of bladder morphology and urothelium microarchitecture, maintaining an adequate level of animal health and welfare while monitoring the onset of urinary tract infections through the sterile collection of urine in long-lasting experiments.