Endoplasmic Tubules Research Articles

Electron Microscope Evaluation of late changes in the nerve fibers and neurons induced by Sciatic nerve section in rabbits

The aim of the study was to demonstrate late changes occurs after Sciatic nerve section [nerve fibers and their associated neurons]. Five adult rabbits were used in this study. Sciatic nerve was sectioned under general anesthesia. After ninety days, all animals were sacrificed and samples were taken from ventral horn of spinal cord, dorsal root ganglion at L₇ segment level and from sciatic nerve for electron microscope evaluation. The results revealed different changes include: separation of the myelin sheath lamellae within ventral horn, the Nissl bodies were scattered within sensory neuron thoughout the cytoplasm specially at the periphery, the cytoplasm contain numerous closed vesicles of different size associated with endoplasmic tubules and the myelin sheath usually forming a loop, axons seemed relatively smaller than normal. All of which are common features of axonal atrophy

Sexual reproduction in the compound ascidian Diplosoma listerianum (Tunicata). I. Metamorphosis, storage and phagocytosis of sperm in female duct

In the colonial ascidian Diplosoma listerianum (collected in the Lagoon of Venice in 1986 and 1991), ovulating eggs detach themselves from the ovary wall and segregate in the tunic without exposure to seawater. With the aim of finding evidence of the pathway followed by spermatozoa to approach the oocyte, histological and ultrastructural observations were made. The results showed that the hollow ovary elongates in a “fertilization canal” which flanks the sperm duct and opens externally, next to the anus. Intercellular extended tight junctions isolate the lumen of this canal from the blood. Sperm were found in the fertilization canal, both free and in intracellular vacuoles of wandering cells (phagocytes). These sperm showed differences in comparison to those from the sperm duct, which are possible signs of a sperm reaction. The main modifications were shown by the “dense groove”, a narrow invagination of the plasmalemma bound to the nuclear envelope by dense material. In non-modified sperm, the groove runs spirally all along the head, while in those in the fertilization canal, it coils in the anterior half of the head, pressing back the long mitochondrion and endoplasmic tubules. These modifications were interpreted to be result of the release of the dense groove, considered to be a sort of stretched, contractile spring. The presence of sperm in the fertilization canal and particularly in phagocytes is discussed in relation to the capacity for exogenous sperm storage by zooids and to the necessity of waste clearance in order for successive waves of fresh sperm to be able to move towards fully grown oocytes. The origin of the female fertilization canal, the role of its tight junctions, and the complex sperm morphology are discussed as adaptations to internal fertilization in D. listerianum.

The Nucleus in the Spores of Rhinosporangium seeberi

Rhinosporidiosis is a disease occurring usually in the tropics and is characterized by the production of nasal polyps supposedly caused by a fungus, Rhinosporangium seeberi, which was claimed after light microscopic studies to proliferate by “amitotic” division of the nucleus. The organism was studied electron microscopically and the spores were found to be bound by a non-collagenous wall enclosing a variety of vesicles, some containing smooth amorphous material, others coiled threads, and still others dark granules. Typically mitochondria, endoplasmic tubules, Golgi, and a membrane-bound nucleus were not seen although a few rudimentary membrane-bound spaces are present. These features as well as failure to culture the organism cast doubts about its taxonomic position, and it seemed the organism was essentially some nucleic acid complex organizing mucopolysaccharides in subepithelial zones in the nasal mucous membrane.