Introduction and Objective: The skin is an important organ in aquatic animals. Owing to its specialized cells and structures, in addition to protecting against environmental factors, it contributes to osmotic balance, sensory perception, and the secretion of certain substances. Skin health and structural changes reflect the overall health of fish and are important for understanding disease processes and environmental effects. Therefore, understanding fish skin and its structural components is important. In this study, the skin of the Mesopotamian barb was investigated using histological, histochemical, immunohistochemical, and surface ultrastructural approaches.Materials and Methods: Six adult female Mesopotamian barb specimens were collected from the Sirwan River at the Qeshlaq Dam, Sanandaj (latitude: 35.4167° N; longitude: 46.9833° E). Approximately 1 × 1 cm skin specimens were collected from the dorsal and ventral regions of the mid-body and placed in fixative. Following fixation and tissue processing, sections were stained using routine and special techniques, including Masson’s trichrome, periodic acid–Schiff (PAS), and Alcian blue, and examined by light microscopy. Tissue sections were also subjected to immunohistochemical staining to investigate S100, Vimentin, and CK AE1 expression. Images were captured using a digital camera. Histometric measurements were performed using ImageJ, and the data were statistically analyzed. Additional dorsal and ventral skin samples were collected and, following fixation and dehydration, sent to the scanning electron microscopy laboratory for processing and imaging.Results: The skin of the Mesopotamian barb consisted of three structural layers: the epidermis, dermis, and hypodermis. The epidermis consisted of living, non-keratinized stratified epithelial tissue composed of columnar to cuboidal, polygonal, and flattened squamous cells. Goblet and club secretory cells were also observed. The dermis consisted of loose and dense connective tissue and contained blood vessels, pigmented cells, and scales. The hypodermis connected the dermis to the muscular bundles of the trunk. Histometric results showed no significant difference in epidermal thickness between dorsal and ventral surfaces (p > 0.05). Goblet cells were more numerous dorsally, whereas club cells were more numerous ventrally; however, neither difference was significant (p > 0.05). Melanophores were significantly more numerous dorsally (p < 0.05). Goblet cells were significantly more numerous than club cells in both dorsal and ventral epidermis (p < 0.05).Immunohistochemical reactivity of CK AE1, Vimentin, and S100 was evaluated in dorsal and ventral skin. CK AE1 showed the most prominent reaction, with moderate to strong cytoplasmic immunoreactivity predominantly in epidermal epithelial cells. Vimentin immunoreactivity was weak and mainly observed in scattered cell populations in the dermis and among epithelial cells near the basement membrane. S100 immunoreactivity was negative.Scanning electron microscopy revealed the arrangement of scales on the skin surface and their posterior regions covered by the epidermis, as well as microridges of surface cells and apical pores between them. Scale surface features included circular ridges and transverse grooves, with an arrangement similar to cycloid scales of other species of the same family.Overall, the general histological structure of the skin was similar between dorsal and ventral surfaces. The histological, histochemical, and ultrastructural characteristics were also similar to those reported in other freshwater fish. Differences in the intensity and distribution of immunostaining indicate that IHC results in fish should be interpreted considering the marker type, target cell population, and species-specific characteristics.

Abstract This study investigates the morphological, morphometric characteristics of thoracic and lumbar intervertebral discs (IVD) in guinea pigs. The main objective of this research is to provide baseline data for comparative studies in veterinary and medical fields, especially in relation to common lumbar diseases. In this study, 5 guinea pigs were examined and morphometric parameters were measured using micro-CT images and macroscopic dissection   and compared with each others. The results showed that 13 thoracic and 6 lumbar discs were identified in guinea pigs. Thoracic discs change from a round shape in the T1-T3 region to triangular and heart-shaped structures in the T4-T13 region, while lumbar discs have a more consistent heart shape. Morphometric analysis revealed statistically significant differences. Lumbar discs were larger than thoracic discs in lateral, dorsal dimensions, and disc area, annulus fibrosus, and nucleus pulposus. In particular, a significant increase in lateral width and disc area was observed at lumbar L5 and L6. Histologically, both disc types had well-organized nucleus pulposus, annulus fibrosus, and endplates. The endplates were composed of hyaline cartilage, fibrocartilage, calcified cartilage, and secondary ossification centers with large vascular channels. Finally, this study demonstrates that although thoracic and lumbar intervertebral discs in guinea pigs retain key features histologically, their distinct morphological and morphometric features reflect adaptation to biomechanical demands. However, due to fundamental differences between humans and guinea pigs, the use of this species as a research model for human intervertebral discs should be done with caution.. Keywords: Guinea pig, Intervertebral disc, pine, roRdent, Micro-CT   

abstract Dislocation of the patella is one of the main causes of lameness in dogs and is one of the most common reasons that send pets to the operating room. In this condition, the patella bone is out of its normal position and the movement of the animal is difficult. Although this condition also occurs in cats, most of the reports are seen in dogs, especially small breed dogs. Dislocation of the patella bone, if it worsens, prevents the normal activity of dogs and creates a big problem for them and their owners. Its abundance statistics have been studied by various researchers. However, despite the growing trend of keeping dogs in the last few years, no information regarding the investigation of this condition in Kermanshah city was found during the search in the available scientific source