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- Englezou, Pavlos C., et al.
(författare)
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Mitochondrial involvement in sensory neuronal cell death and survival
- 2012
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 221:4, s. 357-367
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Tidskriftsartikel (refereegranskat)abstract
- Peripheral nerve injuries (PNI) are continuing to be an ever-growing socio-economic burden affecting mainly the young working population and the current clinical treatments to PNI provide a poor clinical outcome involving significant loss of sensation. Thus, our understanding of the underlying factors responsible for the extensive loss of the sensory cutaneous subpopulation in the dorsal root ganglia (DRG) that occurs following injury needs to be improved. The current investigations focus in identifying visual cues of mitochondria-related apoptotic events in the various subpopulations of sensory cutaneous neurons. Sensory neuronal subpopulations were identified using FastBlue retrograde labelling following axotomy. Specialised fluorogenic probes, MitoTracker Red and MitoTracker Orange, were employed to visualise the dynamic changes of the mitochondrial population of neurons. The results reveal a fragmented mitochondrial network in sural neurons following apoptosis, whereas a fused elongated mitochondrial population is present in sensory proprioceptive muscle neurons following tibial axotomy. We also demonstrate the neuroprotective properties of NAC and ALCAR therapy in vitro. The dynamic mitochondrial network breaks down following oxidative exposure to hydrogen peroxide (H2O2), but reinitiates fusion after NAC and ALCAR therapy. In conclusion, this study provides both qualitative and quantitative evidence of the susceptibility of sensory cutaneous sub-population in apoptosis and of the neuroprotective effects of NAC and ALCAR treatment on H2O2-challenged neurons.
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| 2. |
- Hart, Andrew McKay, et al.
(författare)
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Primary sensory neurons and satellite cells after peripheral axotomy in the adult rat : timecourse of cell death & elimination
- 2002
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Ingår i: Experimental Brain Research. - : Springer-Verlag New York. - 0014-4819 .- 1432-1106. ; 142:3, s. 308-318
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Tidskriftsartikel (refereegranskat)abstract
- The timecourse of cell death in adult dorsal root ganglia after peripheral axotomy has not been fully characterised. It is not clear whether neuronal death begins within I week of axotomy or continues beyond 2 months after axotomy. Similarly, neither the timecourse of satellite cell death in the adult, nor the effect of nerve repair has been described. L4 and L5 dorsal root ganglia were harvested at 1-14 days, 1-6 months after sciatic nerve division in the adult rat, in accordance with the Animals (Scientific Procedures) Act 1986. In separate groups the nerve was repaired either immediately or following a 1-week delay, and the ganglia were harvested 2 weeks after the initial transection. Microwave permeabilisation and triple staining enabled combined TUNEL staining, morphological examination and neuron counting by the stereological optical dissector technique. TUNEL-positive neurons, exhibiting a range of morphologies, were seen at all timepoints (peak 25 cells/group 2 weeks after axotomy) in axotomised ganglia only. TUNEL-positive satellite cell numbers peaked 2 months after axotomy and were more numerous in axotomised than control ganglia. L4 control ganglia contained 13,983 (SD 568) neurons and L5, 16,285 (SD 1,313). Neuron loss was greater in L5 than L4 axotomised ganglia, began at I week (15%, P=0.045) post-axotomy, reached 35% at 2 months (P<0.001) and was not significantly greater at 4 months or 6 months. Volume of axotomised ganglia fell to 19% of control by 6 months (P<0.001). In animals that underwent nerve repair, both the number of TUNEL-positive neurons and neuron loss were reduced. Immediate repair was more protective than repair after a 1-week delay. Thus TUNEL positivity precedes actual neuron loss, reflecting the time taken to complete cell death and elimination. Neuronal death begins within I day of peripheral axotomy, the majority occurs within the first 2 months, and limited death is still occurring at 6 months. Neuronal death is modulated by peripheral nerve repair and by its timing after axotomy. Secondary satellite cell death also occurs, peaking 2 months after axotomy. These results provide a logical framework for future research into neuronal and satellite cell death within the dorsal root ganglia and provide further insight into the process of axotomy induced neuronal death.
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| 3. |
- Hart, Andrew McKay, et al.
(författare)
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Systemic acetyl-L-carnitine eliminates sensory neuronal loss after peripheral axotomy : a new clinical approach in the management of peripheral nerve trauma
- 2002
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Ingår i: Experimental Brain Research. - : Springer-Verlag New York. - 0014-4819 .- 1432-1106. ; 145:2, s. 182-189
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Tidskriftsartikel (refereegranskat)abstract
- Several hundred thousand peripheral nerve injuries occur each year in Europe alone. Largely due to the death of around 40% of primary sensory neurons, sensory outcome remains disappointingly poor despite considerable advances in surgical technique; yet no clinical therapies currently exist to prevent this neuronal death. Acetyl-L-carnitine (ALCAR) is a physiological peptide with roles in mitochondrial bioenergetic function, which may also increase binding of nerve growth factor by sensory neurons. Following unilateral sciatic nerve transection, adult rats received either one of two doses of ALCAR or sham, or no treatment. Either 2 weeks or 2 months later, L4 and L5 dorsal root ganglia were harvested bilaterally, in accordance with the Animal (Scientific Procedures) Act 1986. Neuronal death was quantified with a combination of TUNEL [TdT (terminal deoxyribonucleotidyl transferase) uptake nick end labelling] and neuron counts obtained using the optical disector technique. Sham treatment had no effect upon neuronal death. ALCAR treatment caused a large reduction in the number of TUNEL-positive neurons 2 weeks after axotomy (sham treatment 33/group; low-dose ALCAR 6/group, P=0.132; high-dose ALCAR 3/group, P<0.05), and almost eliminated neuron loss (sham treatment 21%; low-dose ALCAR 0%, P=0.007; high-dose ALCAR 2%, P<0.013). Two months after axotomy the neuroprotective effect of high-dose ALCAR treatment was preserved for both TUNEL counts (no treatment five/group; high-dose ALCAR one/group) and neuron loss (no treatment 35%; high-dose ALCAR -4%, P<0.001). These results provide further evidence for the role of mitochondrial bioenergetic dysfunction in post-traumatic sensory neuronal death, and also suggest that acetyl-L-carnitine may be the first agent suitable for clinical use in the prevention of neuronal death after peripheral nerve trauma.
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| 4. |
- Jivan, Sharmila, et al.
(författare)
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The effects of delayed nerve repair on neuronal survival and axonal regeneration after seventh cervical spinal nerve axotomy in adult rats.
- 2006
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 170:2, s. 245-254
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Tidskriftsartikel (refereegranskat)abstract
- It has been proposed clinically that delayed surgery after traumatic brachial plexus injury may adversely affect functional outcome. In the present experimental study the neuroprotective and growth-promoting effects of early and delayed nerve grafting following proximal seventh cervical spinal nerve (C7) axotomy were examined. The ventral branch of C7 spinal nerve was transected and axons projecting out of the proximal nerve stump were labelled with Fast Blue (FB). At the same time, the biceps brachii muscle was denervated by transecting the musculocutaneous nerve at its origin. Neuronal survival and muscle atrophy were then assessed at 1, 4, 8 and 16 weeks after permanent axotomy. In the experimental groups, a peripheral nerve graft was interposed between the transected C7 spinal nerve and the distal stump of the musculocutaneous nerve at 1 week [early nerve repair (ENR)] or 8 weeks [delayed nerve repair (DNR)] after axotomy. Sixteen weeks after nerve repair had been performed, a second tracer Fluoro-Ruby (FR) was applied distal to the graft to assess the efficacy of axonal regeneration. Counts of FB-labelled neurons revealed that axotomy did not induce any significant cell loss at 4 weeks, but 15% of motoneurons and 32% of sensory neurons died at 8 weeks after injury. At 16 weeks, the amount of cell loss in spinal cord and dorsal root ganglion (DRG) reached 29 and 50%, respectively. Both ENR and DNR prevented retrograde degeneration of spinal motoneurons and counteracted muscle atrophy, but failed to rescue sensory neurons. Due to substantial cell loss at 8 weeks, the number of FR-labelled neurons after DNR was significantly lower when compared to ENR. However, the proportion of regenerating neurons among surviving motoneurons and DRG neurons remained relatively constant indicating that neurons retained their regenerative capacity after prolonged axotomy. The results demonstrate that DNR could protect spinal motoneurons and reduce muscle atrophy, but had little effect on sensory DRG neurons. However, the efficacy of neuroprotection and axonal regeneration will be significantly affected by the amount of cell loss already presented at the time of nerve repair.
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| 5. |
- Welin, Dag, 1978-, et al.
(författare)
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Survival and regeneration of cutaneous and muscular afferent neurons after peripheral nerve injury in adult rats
- 2008
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 186, s. 315-323
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Tidskriftsartikel (refereegranskat)abstract
- Peripheral nerve injury induces the retrograde degeneration of dorsal root ganglion (DRG) cells, which affects predominantly the small-diameter cutaneous afferent neurons. This study compares the time-course of retrograde cell death in cutaneous and muscular DRG cells after peripheral nerve transection as well as neuronal survival and axonal regeneration after primary repair or nerve grafting. For comparison, spinal motoneurons were also included in the study. Sural and medial gastrocnemius DRG neurons were retrogradely labeled with the fluorescent tracers Fast Blue (FB) or Fluoro-Gold (FG) from the homonymous transected nerves. Survival of labeled sural and gastrocnemius DRG cells was assessed at 3 days and 1-24 weeks after axotomy. To evaluate axonal regeneration, the sciatic nerve was transected proximally at 1 week after FB-labeling of the sural and medial gastrocnemius nerves and immediately reconstructed using primary repair or autologous nerve grafting. Twelve weeks later, the fluorescent tracer Fluoro-Ruby (FR) was applied 10 mm distal to the sciatic lesion in order to double-label sural and gastrocnemius neurons that had regenerated across the repair site. Counts of labeled gastrocnemius DRG neurons did not reveal any significant retrograde cell death after nerve transection. In contrast, sural axotomy induced a delayed loss of sural DRG cells, which amounted to 22% at 4 weeks and 43-48% at 8-24 weeks postoperatively. Proximal transection of the sciatic nerve at 1 week after injury to the sural or gastrocnemius nerves neither further increased retrograde DRG degeneration, nor did it affect survival of sural or gastrocnemius motoneurons. Primary repair or peripheral nerve grafting supported regeneration of 53-60% of the spinal motoneurons and 47-49% of the muscular DRG neurons at 13 weeks postoperatively. In the cutaneous DRG neurons, primary repair or peripheral nerve grafting increased survival by 19-30% and promoted regeneration of 46-66% of the cells. The present results suggest that cutaneous DRG neurons are more sensitive to peripheral nerve injury than muscular DRG cells, but that their regenerative capacity does not differ from that of the latter cells. However, the retrograde loss of cutaneous DRG cells taking place despite immediate nerve repair would still limit the recovery of cutaneous sensory functions.
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