Biomedical subjects

Melanie L McEwen

Publications and source records attributed to Melanie L McEwen.

4 recordsLinked to original sources

PubMed2006

Quantification of locomotor recovery following spinal cord contusion in adult rats.

Injury to the spinal cord not only disrupts the functioning of spinal circuits at the site of the impact, but also limits sensorimotor function caudal to the level of the lesion. Ratings of gross locomotor skill are generally used to quantify locomotor recovery following spinal cord injury (SCI). The purpose of this study was to assess behavioral recovery following SCI with three tasks: (1) BBB ratings, (2) walking on a horizontal ladder, and (3) footprint analyses. Behavioral testing was conducted for 6 postoperative weeks, and then the spinal cords were processed for the amount of white matter spared. As expected, BBB ratings dramatically decreased and then improved during recovery. The number of hindlimb foot-faults on the horizontal ladder increased after injury and remained elevated during the recovery period. Footprint analyses revealed that sham-control rats used several different gaits to cross the runway. In contrast, the locomotor function of rats with a SCI was impaired throughout the postoperative period. Some locomotor parameters of the injured rats improved slightly (velocity, stride length, stride duration, stance duration), some did not change (interlimb coordination, swing duration, forelimb base of support, hindpaw angle), and others declined (hindlimb base of support) during the recovery period. Together, these results show that gross locomotor skill improved after SCI, while recovery of fine locomotor function was more limited. Multiple tests should be included in future experiments in order to assess gross and fine changes in sensorimotor function following SCI.

Animals↗

PubMed2005

A mapping study of caspase-3 activation following acute spinal cord contusion in rats.

Spinal cord injury (SCI) initiates a cascade of biochemical changes that results in necrotic and apoptotic cell death. There is evidence that caspase-3 activation and apoptotic cell death occur within hours after SCI. However, the time course and cellular localization of activated caspase-3 has not been examined. Such information is essential because caspase-3-independent apoptotic pathways do exist. In this experiment, we describe the distribution of and cell types containing activated caspase-3 at 4 hr, 1 day, 2 days, 4 days, and 8 days following SCI in rats. Numerous caspase-3-positive cells were observed at 4 hr and 1 day postinjury and colocalized most often with CC1, a marker for oligodendroglia. Both markers disappeared near the injury epicenter over the next several days. Activated caspase-3 was again present in the injured spinal cord on postoperative day 8, which coincided with a reemergence of CC1-positive cells. Many of these CC1-positive cells again colocalized activated caspase-3. NeuN-positive neurons of the dorsal horn were occasionally immunopositive for activated caspase-3 at early time points. OX42-positive microglia/macrophages rarely contained activated caspase-3. The results indicate a biphasic pattern of caspase-3 activation during the first 8 days postinjury, suggesting that at least two mechanisms activate caspase-3 following SCI. This time-course study provides a framework for investigating and understanding the different signaling events contributing to this biphasic pattern of caspase-3 activation.

Acute Disease↗

PubMed2004

Overexpression of XIAP inhibits apoptotic cell death in an oligodendroglial cell line.

1. This study describes the use of an oligodendroglial cell line (158N) to study the protective effects of X-chromosome-linked inhibitor of apoptosis (XIAP) overexpression. 2. 158N cells were transiently transfected with either pCMV-Myc-XIAP or control pCMV-Myc vector. At 48 h post-transfection, immunoblotting and immunocytochemical staining showed robust myc-XIAP overexpression in pCMV-Myc-XIAP transfected cells relative to pCMV-Myc-transfected cells and normal 158N cells. 158N cells were treated with either 100 nm staurosporine (STS) or 300 microM dopamine (DA) and cell survival/function determined using two cell viability assays. 3. Both STS and DA treatments resulted in increased apoptotic death of pCMV-Myc transfected cells. In contrast, there was significant decrease in apoptotic cell death in cells transfected with pCMV-Myc-XIAP. Finally, XIAP overexpression was found to significantly reduce caspase-3 enzyme activity levels in response to apoptotic stimuli. 4. These results provide evidence that XIAP overexpression promotes cell survival in a non-neuronal cell type derived from the central nervous system. In addition, these data suggest that the 158N oligodendroglial cell line is a suitable tool for transient transfection studies, which is a problem frequently encountered when attempting to introduce genes of interest in cultures of primary oligodendroglia.

Apoptosis↗

PubMed2004

The mitochondrial uncoupling agent 2,4-dinitrophenol improves mitochondrial function, attenuates oxidative damage, and increases white matter sparing in the contused spinal cord.

The purpose of this study was to investigate the potential neuroprotective efficacy of the mitochondrial uncoupler 2,4-dinitrophenol (DNP) in rats following a mild to moderate spinal cord contusion injury. Animals received intraperitoneal injections of vehicle (DMSO) or 5 mg/mL of DNP prior to injury. Twenty-four hours following surgery, mitochondrial function was assessed in mitochondria isolated from spinal cord synaptosomes. In addition, synaptosomes were used to measure indicators of reactive oxygen species formation, lipid peroxidation, and protein oxidation. Relative to vehicle-treated animals, pretreatment with DNP maintained mitochondrial bioenergetics and significantly decreased reactive oxygen species levels, lipid peroxidation, and protein carbonyl content following spinal cord injury. Furthermore, pretreatment with DNP significantly increased the amount of remaining white matter at the injury epicenter 6 weeks after injury. These results indicate that treatment with mitochondrial uncoupling agents may provide a novel approach for the treatment of secondary injury following spinal cord contusion.

2,4-Dinitrophenol↗