Age-related NADPH-diaphorase positive bodies in the lumbosacral spinal cord of aged rats

A comparative assessment of age-related nicotinamide adenine dinucleotide phosphate-diaphorase positivity in the spinal cord and medulla oblongata of pigeons, rats, and mice

Nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase (N-d) positive neurons have been extensively studied across various animals, and N-d neurodegenerative neurites have been detected in some aged animal models. However, detailed knowledge on N-d positivity and aging-related alterations in the spinal cord and medulla oblongata of pigeons is limited. In this study, we investigated N-d positivity and age-related changes in the pigeon's spinal cord and medulla oblongata and compared them to those in rats and mice. Pigeons, had more N-d neurons in the dorsal horn, around the central canal, and in the column of Terni in the thoracic and lumbar segments, with scattered neurons found in the ventral horn of the spinal segments. N-d neurons were also present in the white matter of the spinal cord. Morphometric analysis revealed that the size of N-d soma in the lumbosacral, cervical, and thoracic regions was substantially altered in aged pigeons compared to young birds. Furthermore, the lumbar to sacral segments underwent significant morphological alterations. The main findings of this study were the presence of age-related N-d positive bodies (ANB) in aged pigeons, predominantly in the external cuneate nucleus (CuE) and occasionally in the gracilis and CuEs. ANBs were also identified in the gracile nuclei and spinal cord in the aged rats and mice, whereas in aged rats, ANBs were detected in the CuE spinal nucleus. Immunohistochemistry showed that the age-related alterations occurred in the cell types and neuropeptides in old animals. The results suggest weak inflammatory response and neuronal dysfunction in the spinal cord in aged pigeons. Our results suggested that the ANB could be a potential aging marker for the central nervous system.

De novo aging-related NADPH diaphorase positive megaloneurites in the sacral spinal cord of aged dogs

We investigated aging-related changes in nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) in the spinal cord of aged dogs. At all levels of the spinal cord examined, NADPH-d activities were observed in neurons and fibers in the superficial dorsal horn (DH), dorsal gray commissure (DGC) and around the central canal (CC). A significant number of NADPH-d positive macro-diameter fibers, termed megaloneurites, were discovered in the sacral spinal cord (S1-S3) segments of aged dogs. The distribution of megaloneurites was characterized from the dorsal root entry zone (DREZ) into the superficial dorsal horn, along the lateral collateral pathway (LCP) to the region of sacral parasympathetic nucleus (SPN), DGC and around the CC, but not in the cervical, thoracic and lumbar segments. Double staining of NADPH-d histochemistry and immunofluorescence showed that NADPH-d positive megaloneurites co-localized with vasoactive intestinal peptide (VIP) immunoreactivity. We believed that megaloneurites may in part represent visceral afferent projections to the SPN and/or DGC. The NADPH-d megaloneurites in the aged sacral spinal cord indicated some anomalous changes in the neurites, which might account for a disturbance in the aging pathway of the autonomic and sensory nerve in the pelvic visceral organs.

Age-related change of Iba-1 immunoreactivity in the adult and aged gerbil spinal cord

In the present study, we examined change of ionized calcium-binding adapter molecule 1 (Iba-1) in the adult and aged gerbil spinal cords. Significant change of morphological feature and neuronal cell loss were not observed in both adult and aged spinal cords of gerbil after NeuN immunohistochemistry and Fluoro-Jade B histofluoresce staining. Iba-1-immunoreactive microglia broadly distributed in the spinal cord. Most of Iba-1-immunoreactive microglia showed ramified forms in the adult gerbil cervical and lumbar spinal cords. However, morphological changes of Iba-1-immunoreactive microglia were observed in the cervical and lumbar regions of the aged gerbil spinal cord. These microglia were showed a hypertrophied body with shortened swollen processes which was characteristic of activated microglia. In addition, Iba-1 protein level significantly higher in aged cervical and lumbar spinal cords than those in the adult gerbil. The present study showed an increase of activated forms of Iba-1-immunoreactive microglia and its protein level without marked changes in morphological features and neuronal loss in the aged spinal cord compared to those in the adult gerbil spinal cord. This result suggests that the increase of Iba-1 expression in the aged spinal cord may be closely associated with age-related changes in aged gerbil spinal cord.

Alterations in nitric oxide synthase in the aged CNS

Aging is associated with neuronal loss, gross weight reduction of the brain, and glial proliferation in the cortex, all of which lead to functional changes in the brain. It is known that oxidative stress is a critical factor in the pathogenesis of aging; additionally, growing evidence suggests that excessive nitric oxide (NO) production contributes to the aging process. However, it is still unclear how NO plays a role in the aging process. This paper describes age-related changes in the activity of NADPH-diaphorase (NADPH-d), a marker for neurons containing nitric oxide synthase (NOS), in many CNS regions. Understanding these changes may provide a novel perspective in identifying the aging mechanism.

Increased immunoreactivities of cleaved αII-spectrin and cleaved caspase-3 in the aged dog spinal cord

The activation of caspase-3 is considered to be a reliable marker for apoptotic cell death, and a 120-kDa fragment of αII-spectrin is generated by caspase-3 mediated cleavage of this structural protein. In the present study, we compared cleaved αII-spectrin (120-kDa) and cleaved caspase-3-immunoreactive cells and their protein levels in the cervical (C₅-C₆) and lumbar (L₃-L₄) levels of the spinal cord in adult (1-2 year-old) and aged (10-12 year-old) dogs (German shepherds). Weak cleaved αII-spectrin and cleaved caspase-3 immunoreactivity was found in neurons of the adult group; however, their immunoreactivity was distinctively increased in the neuronal cytoplasm in the aged group compared to those in the adult group, although the distribution pattern of their neurons was similar between the adult and age group. In addition, cleaved αII-spectrin and cleaved caspase-3 levels in the aged spinal cord were markedly increased compared to those in the adult group. These findings suggest that the increases of cleaved αII-spectrin and cleaved caspase-3 immunoreactivity may be related to aging of the spinal cord in dogs.