Adenohypophysis of Nile Tilapia El-Sakhawy et al.

In the present research, the histology of the testes of Nile tilapia were done on 56 males sexually mature Nile tilapia fish collected monthly from the River Nile at Giza over the period from September 2009 to August 2010. The testis of the Nile tilapia during the spring, summer and autumn seasons was surrounded by very thin tunica albuginea. The testicular capsule extended inside the testis to give connective tissue septa. The bulk of the testis was composed of seminiferous tubules. These tubules were surrounded by interstitium. The tubules filled with germinal cysts; contained germinal cells at different stages of development and surrounded by cytoplasmic processes of Sertoli cells. The spermatogenic cells were spermatogonia type A and type B, primary spermatocytes, secondary sperma-tocytes, spermatids and spermatozoa. The interstitium filled the intertubular spaces and was composed mainly of fine collagenous connective tissue which contained abundant Leydig (interstitial) cells and blood capillaries. The testis during winter appeared evacuated from the spermatozoa with no cystic arrangement of the germinal cells. The testis showed different degrees of vacuolation. The tubular lumen contained residual sperms. The vacuoles appeared in the Sertoli cells. Phagocytic cells were observed in close association of the basement membrane of Sertoli cells.

The thymus of Tilapia nilotica (Oreochromis niloticus) was covered by thin capsule with short trabeculae. The parenchyma was differentiated into cortex and medulla; the cortex consisted of dense population of lymphoid cells and few epithelial reticular cells, while the medulla consisted of few lymphoid cells and abundant epithelial reticular cells. Thymic corpuscle-like structures also detected in the medulla. The parenchyma also contained pigmented macrophages and mast cells. The kidney of Tilapia nilotica (Oreochromis niloticus) was differentiated into two parts; head and trunk kidneys. Head kidney could not differentiated into cortex and medulla. The subcapsular region contained haemopoietic tissue. The haemopoietic elements were represented by different types of cells. Non encapsulated melano-macrophage centres were found either sporadic or as clusters. Corpuscle of Stannius was seen embedded in the parenchyma. The trunk kidney was formed of nephrons and interstitial tissue which was represented by haemopoietic tissue, lymphoid tissue and melano-macrophages. The spleen was surrounded by thin capsule. The spleen was composed of red, ill developed white pulp and accumulation of melano-macrophages. The subcapsular region occupied mostly by the red pulp. Also the spleen contained haemopoietic tissue. Some exocrine pancreatic acini were noticed at subcapsular region. Melano-macrophage centres were found around the vascular channels and embedded in the parenchyma. Histological Studies On Some Immune Organs ...

The normal structure of the liver of Gilthead sea bream, an economically valuable marine fish, was studied using LM and electron microscopy.The liver was covered by a thin fibrous connective tissue capsule, and a single layer of mesothelial cells. The parenchyma of the liver was not divided into lobules. The biliary channels and vascular elements seemed to be randomly dispersed throughout the parenchyma. The liver was formed of a mass of cells penetrated by sinusoids. Within the parenchyma, the hepatocytes spread out as irregular cords arranged in two cellular layers surrounded by sinusoids. Hepatic sinusoids were lined by endothelial cells with elongated dark nuclei. The endothelium separates the space of Disse incompletely from the lumen of sinusoids.The hepatocytes were hexagonal in shape, had spherical pale-stained and centrally located nuclei that showed one or more nucleoli. Binucleated cells were sometimes visible. ultrastructurally hepatocytes showed large, spherical and rounded nuclei. The nucleus contained one or more prominent nucleoli. It was pale euchromatic and showed some heterochromatin at the periphery. The microvillus surface of the hepatic cells was clear in the space of Disse, interhepatocytic surface and canalicular surface facing the bile canaliculi. The cytoplasm had abundant amounts of R.E.R while S.E.R. was few. Numerous mitochondria, large amount of glycogen as well as many lipid droplets were also seen.

The ultrastructure features of the pulmonary alveoli of the onehumped camel were basically similar to those described in other animals. The alveoli were lined by squamous type-I pneumonocytes interspersed with large irregular or cuboidal type-II pneumonocytes. They were resting on a thin basal lamina. The interalveolar septum was of variable thickness. It contained the gas exchange capillaries, fibroblasts, plasma cells and mast cells together with many collagenous and elastic fibrils. Alveolar macrophages appeared in most alveolar lumen. Intravascular active monocytes were seen.