Telecommunications network architecture

An abstract generic system model and methodology that form the Telecommunications Network Architecture (TNA) are described. The model represents controls and communication functions required for the transfer of information within a node or a network of nodes providing any service (message, packet, or voice). The architecture can be used to represent the most primitive switching mechanism. The methodology is intended to offer the system designer an appreciation of communication systems, and the ability to trace the impact of modifications.     

Structural observations on the gills of two fresh water teleost fishes, Notopterus notopterus and Colisa fasciatus

1. The structural observations of the gills of Notopterus and Colisa fasciatus have been studied in detail. 2. The gills of Notopterus notopterus and Colisa fasciatus consist of 2 regions: a) Gill head region, and b) Gill lamellae region. Gill head region is covered by epithelial layer possessing the mucous and mast cells. Gill head region consists of bony arch, gill rakers and interbranchial septum. 3. Interbranchial septum is reduced in Notopterus notopterus while it extends near half to the length of the filament in Colisa fasciatus. 4. In both fishes, the adductor muscle, afferent and efferent branchial vessels and gill rays are present in the interbranchial septum area. 5. Gill lamellae region consists of primary and secondary lamellae in both the fishes. 6. In Notopterus notopterus the primary lamellae are compressed flat structures possessing gill rays, 1 afferent and 1 efferent branchial vessel, while in Colisa fasciatus 2 efferent vessels are present. 7. Secondary lamellae are arranged parallel to one another on both sides of the primary lamellae. Secondary lamellae consist of basement membrane, epithelial cells, vascular layer and pillar cells. Mucous and mast cells are also present in this region in case of Notopterus notopterus while only mast cells are present in Colisa fasciatus. 8. Mast cells are eosinophilic, highly granulated in both the fishes.     

Pathogenesis of trimethyltin neuronal toxicity. Ultrastructural and cytochemical observations

The ultrastructural cytopathologic and cytochemical effects of trimethyltin (TMT) neurotoxicity were delineated in hippocampal and pyriform neurons of acutely intoxicated adult rats. TMT produced neuronal necrosis that preferentially involved hippocampal formation pyriform cortex. The first subcellular alterations were multifocal collection of dense-cored vesicles and tubules and membrane-delimited vacuoles in the cytoplasm of the perikaryon and proximal dendrite. Ultrastructural cytochemical examination revealed that the vesicles and tubules had acid phosphatase activity analagous to Golgi-associated endoplasmic reticulum (GERL). Shortly after the appearance of the GERL-like vesicles and tubules, autophagic vacuoles and polymorphic dense bodies accumulated in the neuronal cytoplasm. Some dense bodies appeared to arise from the dense-cored tubules. Neuronal necrosis was characterized by increased electron density of the cytoplasm and large, electron-dense intranuclear masses. Alterations of mitochondria and other organelles were not observed in the early stages of cell injury. No light- or electron-microscopic alterations were found in liver or kidney. Comparable subcellular alterations were observed in adult and neonatal rats chronically intoxicated with TMT. A series of other trialkyl and tricyclic tins and dimethyltin did not produce similar pathologic findings. The GERL-like accumulations are unique in neuronal cytopathology. These findings suggests that GERL and autophagy play an important role in the pathogenesis of TMT-induced neuronal injury.