Parvalbumin in cortical epithelial cells of the pigeon thymus

We examined the distribution of parvalbumin in the pigeon thymus by light and electron microscopic immunohistochemistry. Tissues were also examined by conventional electron microscopy to determine the ultrastructure of immunoreactive cells. Parvalbumin immunoreaction was located in epithelial cells of the cortex, which formed dense mesh-like structures. Parvalbumin-positive epithelial cells were classified into 2 types. The first comprised elongated cells. In these, the nucleus was spindle-shaped, oval, or triangular, with a slightly irregular contour and contained rich heterochromatin peripherally. The cytoplasm was pale and processes extended laterally or ramified among the surrounding thymocytes. This type of cell formed the majority of immunoreactive cells. The other cell type consisted of polygonal epithelial cells. The nucleus was oval with deep indentations. Euchromatin occupied a large part of the nucleus. The cytoplasm contained numerous cell organelles compared with the elongated type, in particular, electron-dense vacuoles of various sizes and often bundles of tonofilaments. Both types of epithelial cell were interconnected by desmosomes. No secretory granules were found in the cytoplasm of elongated or polygonal cells. These results indicate the presence of heterogeneous group of parvalbumin-immunoreactive epithelial cells and suggest the likelihood of different functional roles for parvalbumin in the pigeon thymus

Innervation of NADPH diaphorase-containing neurons correlated with acetylcholinesterase, tyrosine hydroxylase, and neuropeptides in the pigeon cloaca

The motility of the avian cloaca is under neural control, but little is known about the neural network that accomplishes this function. This present study was designed to determine the distribution of nitric oxide-synthesising neurons in the pigeon cloaca by enzyme histochemistry for reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d). NADPH-d-positive staining was seen in the neurons and fibres in the cloaca. The highest density of nerve fibres was noted in the coprodeum and the lowest in the proctodeum. In the coprodeum, NADPH-d neurons were found singly, formed small groups of 2–10 neurons, or were seen in plexuses in the muscle layer, lamina propria, or around the arterioles. Several NADPH-d-positive neurons were also observed in the ganglia of the cloaca. NADPH-d fibres ran in the muscle layer, lamina muscularis mucosae and lamina propria, or surrounded blood vessels. The distribution pattern of acetylcholinesterase (AChE)-stained neurons and fibres in the cloaca was similar to that of NADPH-d. Double staining for NADPH-d and AChE showed colocalisation of the 2 enzymes in many neurons of the cloaca. Tyrosine hydroxylase (TH)-immunoreactive nerve fibres originating outside the cloaca were also noted. In the urodeum and proctodeum, neurons or fibres positive for NADPH-d, AChE or TH were scattered in the lamina propria. Nerve fibres immunoreactive for calcitonin-gene related peptide, galanin, methionine-enkephalin, substance P, and vasoactive intestinal peptide were found sparsely in the cloaca. Our results demonstrate that nitrergic neurons constitute a subpopulation which is closely associated with the cholinergic system in the pigeon cloaca

Cerebral Venous Air Embolism due to a Hidden Skull Fracture Secondary to Head Trauma

Cerebral venous air embolism is sometimes caused by head trauma. One of the paths of air entry is considered a skull fracture. We report a case of cerebral venous air embolism following head trauma. The patient was a 55-year-old man who fell and hit his head. A head computed tomography (CT) scan showed the air in the superior sagittal sinus; however, no skull fractures were detected. Follow-up CT revealed a fracture line in the right temporal bone. Cerebral venous air embolism following head trauma might have occult skull fractures even if CT could not show the skull fractures