Background: The golden hamster is a choice model for investigating many visceral and splenic infections and neoplastic and retrospective lesions. Aim: To study hamsters' spleen's morphological, histological, and histochemical structure. Methods: Samples were collected from eight healthy adult golden hamsters and then fixed with 10% buffered formalin. Later, samples were processed, sectioned, and stained with Hematoxylin and Eosin as well as Masson’s Trichrome stain. Other slides were further stained with Periodic Acid Schiff and Alcian blue 2.5 stain (PAS) for histochemical evolution; the gross measurement was performed for the splenic length, width, and thickness, while the histological measures included the splenic capsular and trabecula thickness, diameter of white pulp follicles, splenic sinusoids and central arteries and proportion of white and red pulps. Results: The macroscopic findings revealed that the spleen was red-brown lanciform on the left side of the dorsolateral abdominal wall. The morphological measurements for splenic length, width, and thickness were 26.6 ± 7.67, 4.17 ± 1.65, and 1.70 ± 0.01 mm, respectively. The histological observations showed that the splenic capsule was composed of two layers (serosal and subserosal). The inner layer sends trabeculae dividing the splenic parenchyma irregularly, and the splenic parenchyma comprises the white and red pulp. The white pulp follicles included the mantle, marginal zones, and the PALS (periarterial lymphatic sheath), while the red pulp constituted splenic cords and sinuses. The histomorphological findings showed that white pulp follicles and the central artery mean diameter were 252.62 ± 8.07 µm and 54.45 ± 0.36 µm respectively, the proportion of white to a red pulp was 0.49 ± 0.01, the splenic capsule, trabecula and the wall of splenic arteries showed an intense positive activity to PAS stain and negative or weak in other splenic structures. Conclusion: The similarities and differences in the spleen between the laboratory animals and hamsters were apparent in this article, so understanding the morphological and histological structure of the spleen presents significant assistance with species identification to select the appropriate experimental animal model in future medical research

Caeca are outpouches of the alimentary canal originating at the junction of the small and large intestine. The histology and ultrastructure of these caeca in birds reveal a considerable specific variation, which likely reflects functional differences among avian species. Each caecum divides into three regions or zones; proximal, middle and distal. In this work, a comparative study by light and transmission electron microscopy is carried out on the three different caecal regions of quail, duck and owl. The histological results show the presence of caecal tonsils in the beginning of the proximal region of quail caeca only. These tonsils are consisting of the aggregated masses of lymphocyte, forming a multiple nodules and encapsulated by muscle fibers. However the duck caeca were devoid of caecal tonsils and all caecal regions contained aggregation of lymphoid nodules while, in the owl caeca the lymphoid tissue found only in the proximal zone. The presence and shape of villi, plicae circulars and crypts were explained in detail. The ultra structure of the caecal regions of the each bird explained how the proximal perform its absorptive function more than the middle and distal regions through the presence of different organelles such as microvilli and mitochondria. Histology and ultra structure of the caeca in the three birds revealed some important facts which may be differ from that established in the past.

The present study aims to elucidate retinal development by analyzing the histomorphological and histomorphometrical parameters in white rabbits (Oryctolagus cuniculus retina). Samples were collected from 25 rabbits divided into five different age groups: 1, 10, 15, 30, and 40 postnatal days (PND). The samples were then sectioned, processed, and stained with Hematoxylin and Eosin stain, as well as Masson's trichrome stain. Some sections were additionally stained with toluidine blue (TB) stain to detect cell density in the outer and inner nuclear layers. Measurements of retinal layers were performed for morphometric comparison among the age groups. The findings revealed that the total thickness of the retina gradually decreased with age. The thickness of the inner and outer nuclear layers, as well as cellular density, also decreased with the development of the photoreceptor layer (rods and cones). This decrement was accompanied by an elevation of the outer plexiform layer thickness and swelling of the ganglion cell layer, particularly after the opening of the eyelids and the differentiation of the different layers of the retina. The histomorphometry results in the retina showed significant differences in the thickness of its different layers among the five age groups. In conclusion, Retina showed highly active histological development and growth with cellular differentiation and significant measurements differences before and after eyelid opening between 10 -15 PNDs.

No abstract