Studies On Age-Related Morphological Changes In The Lumbar Spinal Cord Of Cat

The spinal cord is a lower reflex center and the passageway of excitatory conduction for the central neural system (CNS). Age-related morphological changes in the spinal cord may greatly impact its physiological function. In this paper, we compared the structures of the lumbar spinal cords in young adult and old cats in order to accumulate morphological data for further research on spinal aging.1. The Lumbar 6 (L₆) spinal cord were chosen from young adult (1-3 years old, 2-2.5 Kg) and old cats (12 years old, 3-3.5 Kg). Neurofilament (NF) immunohistochemistry was used for characterizing the nerve fibres in all the funiculus of white matter, and the transmission electron microscopic technology was applied to observe the ultrastructures of the fibres in funiculus posterior. The numbers of the fibres in all the funiculus were counted from the NF-stained sections, and the diameters of the mylinated fibres and their axons from ultrathin sections were measured. All results were subjected to statistical analysis, and diameter spectrum of the fibres (D) and their axons(d) were quantitatively described in the diameter spectrum both for young and old cats. Compared with the young adult cats, the old cats showed a significantly lower density of the nerve fibres in all the funiculus (p<0.01) accompanied with a weaker stain of NF-immunoreaction.In addition, the mylinated fibres in old cats exhibited disordered distribution, and the myelin sheaths exhibited abnormity,such as sheath loosening, myelin ballons and myelin hyperplasy. Observed from the diameter spectrum, the old cats showed a considerably decreased number of thin nerve fibres, while the thick fibres exhibited a thin axon accompanied with a relatively thickened myelin sheath when compared with the young adults. And a declined d/D was observed in the old cats. The above results suggested a significant loss of the nerve fibres, atrophy of axon and hyperplasia of the myelin sheath in the white matter during spinal senescence, which might lead to a degradation of relevant conduction processing in the spinal cord of senescent cats.2. In order to investigate age-related morphological changes of glial cells in the white matter of the lumbar spinal cord in young adult and old cats, several techniques were used: (1) Modified Holzer crystal violet staining to show all the glial cells; (2) Immunoreaction of glial fibrillary acid protein (GFAP) to exhibit the astrocytes; (3) Golgi...