Ghrelin hormone is a novel 28 -amino acid has recently discovered in birds in 1999. Ghrelin is a hormone produced by endocrine cells in the gastrointestinal tract. It stimulates growth hormone secretion, promotes food intake and energy expenditure. The distribution and morphologic characteristics of ghrelin -containing cells in the gastrointestinal tract of goose, ducks, chicken, quails and ostrich was investigated by immunocytochemistry. Ghrelin -immunopositive (ip) cells were located in the mucosa of the proventriculus, duodenum, jujenum, ileum and cecum of goose and duck, while in chicken, the ghrelin positive cells were mainly localized in the proventriculus and few cells were scattered in the small and large intestine. In quail and ostrich, the cells only found in the proventriculus. The numbers of the positive cells were numerous in goose and duck, than that in the chicken, quails and ostrich.

The present investigation examined histogenesis of epithelial, stromal and angiogenic elements of the prenatal camel permanent or metanephric kidney. The primitive metanephros was first observed at the 13-mm crown vertebral rump length (CVRL) stage as an ovoid structure composed of a centrally located epithelial ureteric bud and peripheral circumscribed masses of undifferentiated mesenchymal cells. The first morphological evidence of glomerulogenesis was observed at the 28-mm CVRL stage. Developing renal corpuscles became obvious at the 35-mm CVRL stage. At the 60-mm CVRL stage, the epithelial renal pelvis gave rise to tubular branches that extended towards the cortical zone. These branches represented the presumptive collecting ducts. Differentiation of renal tubules into the proximal and distal convoluted tubules was observed at the 95-mm CVRL stage. At the 130-mm CVRL stage, the renal medulla was clearly delineated into medullary pyramids, which in association with the corresponding cortical caps formed the morphological basis of the renal lobar formation. A gradual nephrogenic decline was noticed from the 940-mm CVRL on; however, the process of nephrogenesis persisted throughout all the studied foetal stages.

The current study was conducted to examine the one-humped camel (Camillus dromedarius) extraocular muscles and their innervation. Furthermore, the S-100 immuno-expression within these muscle fibers was analyzed. Fourteen eyeballs, from native Egyptian camels (of both sex), were collected. Processing and preparation of the obtained tissue samples took place after being immersed in 10% neutral buffered formalin. After that, they sectioned, and then subjected to the following stains; Hematoxylin & Eosin (H&E) for determination of muscle spindle, nerve trunk, and Golgi tendon organ, PAS and Alciane blue for detection of mucopolysaccharides, and silver stain to examine muscle fibers and nerve trunk affinity. The obtained results showed that the extraocular muscles consisted of seven muscles: four recti, two obliques, and one retractor bulbi muscle. Each muscle had a muscle spindle that was encapsulated with a connective tissue capsule with intrafusal muscle and paraxial space. As well as, the Golgi tendon organ was found at the musculotendinous junction. Immuno-expression of the seven muscles showed varying degrees of immunostaining affinity to the S-100 protein.

The histological and histochemical studies were carried out on 60 camel embryos and foetuses eye balls of different Crown Vertebral Rump Length (CVRL). Paraffin sections were prepared and subjected to different stains. The present study revealed that, the optic pit was detected at 0.8 cm CVRL, as shallow groove on either side of the neural folds. The optic vesicle was observed at 1.5 cm CVRL, comprising from neuroectodermal cells, which became modified into a crescentic cup-like structure representing the optic cup at 2 cm CVRL. The optic cup was comprised from outer pigmented epithelium and the inner neuroblastic layer. The ganglion cells were distinctly differentiated at 6 cm CVRL, which separated from neuroblastic cells by the inner plexiform layer. The inner nuclear layer was firstly observed at 30 cm CVRL, which exhibited its full differentiation at 35 cm CVRL and became separated from the outer nuclear layer by the outer plexiform layer. First appearance of the photoreceptor cells was observed at 55 cm CVRL, which differentiated into outer and inner segments at 74 cm CVRL. All the layers of the retina were completely differentiated at 98 cm CVRL, comprising ten retinal layers.

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