Ultrastructural studies on the nuclear elements in differentiating and degenerative ciliated olfactory neuron of Pseudapocryptes lanceolatus (Gobiidae: Oxudercinae)

Abstract

The cellular event of neurogenesis and neural degeneration of ciliated sensory receptor neuron within the adult olfactory neuroepithelial system has been studied in Pseudapocryptes lanceolatus (Bloch and Schneider, 1801) under light microscope (LM), fluorescence microscope and transmission electron microscope (TEM: Morgagni 268D) respectively. The unilamellar olfactory apparatuses of P. lanceolatus were dissected and fixed in 2.5% glutaraldehyde and 4% paraformaldehyde in 0.1 M phosphate buffer (pH 7.2–7.4) at 4 °C for microscopical studies. The LM study indicates that the progenitor basal cell proliferates to form electron lucent basal cell which differentiates into ciliated sensory receptor neuron within the olfactory neuroepithelium. Investigation under fluorescence microscope using Acridine Orange revealed that the nuclear elements in differentiating stages of electron lucent basal cell, mature and degenerating sensory receptor cell show notable features of gradual condensation. TEM study indicates the subsequent condensation of chromatin granules (diameter ranging from 10 nm–20 nm to 15 nm–30 nm) in various differentiating stages of electron lucent basal cell. The mature ciliated sensory receptor cell possesses chromatinized nucleus with large accumulation of chromatin granules (diameter: 20 nm–30 nm) at the peripheral nucleoplasm whereas degenerating sensory receptor cell possesses fragmented chromatin fibers. Therefore, these distinctive features of chromatin condensation are assumed to be a prime subcellular indicator of neural aging of olfactory sensory receptor cell.