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Immunocytochemical localisation of proteins implicated in Ca2+ and free radical homeostasis in normal and axotomised cat spinal motoneurones: A segmental comparison with reference to amyotrophic lateral sclerosis

Pearlstone, Alisa Shira; (2000) Immunocytochemical localisation of proteins implicated in Ca2+ and free radical homeostasis in normal and axotomised cat spinal motoneurones: A segmental comparison with reference to amyotrophic lateral sclerosis. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Motoneurones of Onufs nucleus (ON) in the sacral spinal cord enjoy relative resistance to degenerative motor conditions. It has been suggested that, in the case of amyotrophic lateral sclerosis (ALS), this resistance may relate to the differences between these motoneurones and other somatic motoneurones in the levels of Ca2+ buffering proteins ordinarily present. Ca2+ regulation and free radical homeostasis are central to the current understanding of the causes of neuronal death in ALS and therefore six proteins relevant to both of these activities were selected for further investigation in the spinal cord of the adult cat. To determine their localisation and investigate the possibility of segmental differences, immunocytochemical analyses were carried out in cervical, thoracic, lumbar, and sacral segments in the normal cat. In a second set of experiments aimed at characterising the regulation of these proteins after injury in a group of ALS-vulnerable neurones, motoneurones innervating the sartorius muscle were axotomised. Finally, post-axotomy alterations of immunoreactivity levels in Sartorius motoneurones were compared with the alterations seen after axotomy of the pudendal nerve, arising from ON. The proteins examined were calbindin (CaBP-D28k), parvalbumin (PV), calmodulin (CM), calcineurin (CaN), neuronal nitric oxide synthase (nNOS), and superoxide dismutase (SOD). Immunocytochemical labelling of perfusion fixed cat spinal cord revealed high levels of nNOS, SOD, and CaBP-D28k in ON. Full quantitative analysis showed that nNOS immunoreactivity (IR) and CaBP- D28k-IR were significantly higher in sacral motoneurones than motoneurones from cervical, thoracic, or lumbar spinal cord. Axotomised sartorius motoneurones showed significant bilateral decreases in CaBP-D28k-IR, CM-IR, and CaN-IR, and a bilateral increase in nNOS-IR. By contrast, post-axotomy alterations in ON were found to be unilateral. Furthermore, nNOS-IR in axotoniised ON was found to be decreased on the side of the lesion. The higher levels of CaBP-D28k in ON are discussed in the context of the current understanding of the functional importance of CaBP activity. It is suggested that higher levels of nNOS may relate to the possibility that pudendal motoneurones synthesise and release NO as a transmitter substance. Differential post-axotomy regulation of nNOS is hypothesised to reflect post-axotomy transmitter regulation in ON compared to a pure injury response in the sartorius motoneurones, which do not utilize NO as a transmitter. Segmental differences in the laterality of injury responses are considered in the context of segmental variations in bilateral connectivity. These findings are also discussed alongside the concept of differential vulnerability in ALS.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Immunocytochemical localisation of proteins implicated in Ca2+ and free radical homeostasis in normal and axotomised cat spinal motoneurones: A segmental comparison with reference to amyotrophic lateral sclerosis
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10103707
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