The primary motor cortex (M1) contains a somatotopic progression with highly overlapping areas outputting to muscles of the upper limb. This organization is modified by muscle activity and neurological injury such as spinal cord injury (SCI). To date, bilateral M1 organization in controls and SCI has been minimally explored, and no study has examined the cortical territory that directs output to multiple muscles thought to be involved in movement synergies. An initial study was conducted to characterize the bilateral organization and representational overlap for muscles of the upper limb in incomplete spinal cord injury relative to uninjured individuals. Differences in symmetry and amount of overlapping territory were observed between groups, possibly reflecting differences in synergistic muscle use. The second study examined transcallosal communication between the two motor cortices and its role in dynamically modulating motor representations during unilateral contraction. The depth of interhemispheric inhibition (IHI) was examined in a muscle of the right hand by delivering a conditioning stimulus to ipsilateral M1 followed by a test stimulus to contralateral M1. Reduced IHI corresponded to larger cortical territory, a relationship that existed for both contralateral and ipsilateral contraction. These data demonstrate that the magnitude of IHI in a hand muscle predicts the size of the cortical territory occupied by that muscle. We present a mechanistic model to explain these findings that further elucidate the role of interhemispheric communication in shaping motor output. This interaction between transcallosal inhibition and motor output may act as a component to experience-dependent plasticity within M1. By targeting this interaction, it may be possible to facilitate motor learning and performance or promote recovery of function following neurological injury. Further study examining the role of various intracortical circuits on representational plasticity and modulation of these interactions may yield advances in both basic and clinical neuroscience. / Thesis / Master of Science (MSc)

Skeletal muscle is the primary site of glucose disposal in the body, and consequently plays a predominant role in the regulation of blood glucose levels after the ingestion of a meal. Following spinal cord injury (SCI), skeletal muscles below the level of an upper motor neuron lesion undergo marked changes in muscular properties that affect glucose tolerance. Recent studies on individuals with a SCI have reported improved glucose tolerance following periods of electrically-stimulated training. This appears to result from improved muscle morphology and post-exercise insulin sensitivity, and increased GLUT 4 content, enzyme activity, and muscle fiber capillary number. It might be expected that the weight-bearing and greater muscular involvement associated with body-weight support treadmill training (BWSTT) would have an even more profound effect on previously observed responses. The purpose of this study was to investigate whether 6 months of BWSTT improved whole-body glucose tolerance and some of the muscular parameters that are expected to influence glucose metabolism, in a group of 9 individuals with an incomplete SCI. A leg biopsy and a resting, 3 hour oral glucose tolerance test (OGTT) were performed on each subject before and after 6 months of training. Analysis of the muscle biopsy revealed significant increases in post-training muscle fiber size for type I (P=0.01) and type IIa (P=0.05) fibers in comparison to pre-training values. A significant increase in type IIa fiber proportion (P=0.03) and a significant decrease in type IIx fiber proportion (P<0.01) were found following training. In addition, significant increases in post-training GLUT 4 protein content (P<0.01), citrate synthase protein content (P<0.01), and citrate synthase activity (P=0.01) were found in comparison with pre-training values. No change was found in the number of capillaries per fiber after training. Plasma insulin area under the time curve (AUC) during the post-training OGTT significantly decreased (P=0.04) in the subjects as a result of BWSTT. Despite the large decrease in plasma insulin concentration, blood glucose AUC also showed a significant decrease (P<0.01) during the post-training OGTT, indicating a training-induced increase in insulin sensitivity occurred in the subjects. According to the findings, we can speculate that the increase in insulin sensitivity was a result of the increase in muscle GLUT 4 content in the exercised muscles, possibly in combination with an increase in leg muscle mass, as indicated by an increased muscle fiber cross-sectional area. The results are the first in this field to provide evidence that BWSTT leads to beneficial morphological and metabolic changes in skeletal muscle fibers that improve glucose tolerance. / Thesis / Master of Science (MSc)

The purpose of this study was to determine the effects of cessation of a 12-month thrice-weekly body-weight supported treadmill training (BWSTT) program on functional ambulation and aspects of health-related quality of life (HRQL) in individuals with incomplete SCI. Twelve men and women (aged 22-55) with chronic (> 1 year post-injury) incomplete SCI (ASIA B or C) returned for follow-up (FOL) testing 37 weeks (SD 2.1) following their final scheduled BWSTT session. Functional ambulation was compared based on: i) required percentage of body-weight support (%BWS) on the treadmill, ii) preferred treadmill speed and iii) overground walking. Evaluation of HRQL included measures of: i) satisfaction with life, ii) perceived ability to perform activities of daily living (ADL), iii) perceptions of health, and iv) depressive symptomology. Participants were invited to participate in once-weekly BWSTT and twice-weekly fitness training during the FOL period (37 sessions); the actual number of BWSTT sessions attended was only 11.6 (range 0-29) and the total days of exercise was 29.1 (range 0-75). The 12-month BWSTT program resulted in a decrease in the required %BWS (73±10% to 19±12%; p<.01), an increase in treadmill speed (0.5±0.3 to 1.4±0.8 km/h; p<.01), improved overground walking in 4 individuals, and improved group satisfaction with life (p<.05). At FOL, %BWS increased to 35±14% (p<.01), but was still less than at pre-training (p<.01). There were no differences between 12-month and FOL scores on any HRQL-related measures. High exercise adherence during the FOL period had a strong correlation with a positive percent change in perceived ability to perform ADL (r = .70; p<.05), as well as non-significant trends with positive percent change in perceptions of health and negative percent change in depressive symptomology (r = .49; p=.13 and r = .51; p=.ll, respectively). Therefore, even with very limited access to the BWS treadmill, much of the improvement in treadmill walking ability and satisfaction with life following long-term BWSTT in individuals with incomplete SCI can be retained for at least 8 months. Continued exercise participation, however, may contribute to maintain or further improve aspects of HRQL in this population. / Thesis / Master of Science (MS)

Impaired wound healing in SCI patients contributes to the progression in severity of PIs. Best practice guidelines suggest that surgical flap reconstruction is an option for chronic stage 4 PIs that have failed to heal with more conservative measures, but little is known about the epidemiology of surgically reconstructed PIs in SCI patients. Rates of surgical wound complications are high, and cost of management is extensive. Accordingly, this study aims to establish a systematic approach for identifying SCI patients with surgically reconstructed PIs, to facilitate study of predictors of sustained wound closure, quantify costs of surgical reconstruction, and evaluate efficiency of treatment and recovery options. To address gaps in the literature, this study’s objectives were: (1) estimate surgical reconstruction hospital costs for stage 4 PIs in SCI patients and characterize the relationship of demographic, socioeconomic and lifestyle factors to cost at discharge, (2) explore a standardized method of identifying these cases in large databases, (3) identify and validate risk factors for complications at discharge from wound care follow-up, and (4) identify long-term cost and health care utilization of persons with SCI who have undergone surgical flap closure. It proved difficult to identify our own cohort of patients using administrative codes applied, making population-based study using administrative data less than ideal. Factors associated with open incision at three-to-six weeks post-index surgery included number of nursing visits in the previous year, and revision surgery within the six-week follow-up period. The cost of persons with SCI and PI was high one year prior to surgery (look-back) and almost double in the first year look-back. However, significant cost and health care utilization was demonstrated in Year 2 and 3 post-index surgery. Further prospective studies exploring models of health care delivery and addressing some of modifiable risk factors may improve cost-effectiveness and outcomes. / Thesis / Doctor of Philosophy (PhD) / Pressure ulcers, also known as pressure injuries (PI) or bedsores, are a common secondary complication in persons with spinal cord injury (SCI). While surgical closure is an option offered to patients, little is known about the long-term outcomes, including cost and use of health care services following the surgery. Risk factors for complications following surgery are known from a physical/co-morbidity/technique perspective, but environmental and behavioural factors have not been included these studies, and the use of health care administrative databases to accurately identify these patients for research has not been studied. A historical cohort study was conducted at one tertiary care centre in Toronto, Canada to identify known cases of SCI and PI reconstruction. Hospital codes were recorded in an algorithm used to evaluate the accuracy in identifying the known cases in the database. Health care usage and costs were also recorded, and risk factors for complications were also evaluated.

<p dir="ltr">Though mammalian spinal cord injury (SCI) has long been a topic of study, effective therapies that promote functional recovery are not yet available. The axolotl, <i>Ambystoma mexicanum</i>, is a valuable animal model in the investigation of spinal cord regeneration, as this urodele is able to achieve functional recovery even after complete spinal cord transection. Understanding the similarities and differences between the mammalian SCI response and that of the axolotl provides insight into the process of successful regeneration, and bolsters the fundamental knowledge used in the development of future mammalian SCI treatments. This thesis provides a detailed analysis of the ultrastructure of the axolotl meninges, as this has not yet been presented in existing literature, and reveals that the axolotl meninges consist of 3 distinct layers as does mammalian meninges; the dura mater, arachnoid mater, and pia mater. The role of reactive meningeal and ependymal cells is also investigated in regard to the deposition and remodeling of the fibrotic ECM, which is found to be similar in composition to hydrogel scaffolds being studied in mammalian SCI. It is shown that meningeal fibroblasts are the primary source of the extensive fibrillar collagen deposition that fills the entire spinal canal, peaking at approximately 3 weeks post transection and remaining until approximately 5 weeks post transection, and that there is no deposition of type IV collagen within the lesion site. Mesenchymal ependymal cells are shown to contribute to the ECM deposition through the production of glycosaminoglycans that are used in sidechains of both unsulfated and sulfated proteoglycans, while simultaneously remodeling the ECM through the production of MMPs and phagocytosis of cellular debris. Further, this study shows that mesenchymal ependymal cells and a population of foamy macrophages contribute to the degradation of the fibrin clot that forms in the acute phase of injury, and that this fibrin clot provides a necessary and permissive substrate for early mesenchymal outgrowth.</p>

Background: Quantitative imaging surrogates of myelin and axonal integrity using magnetization transfer and diffusion tensor imaging may provide beneficial prognostic details on long-term post-surgical recovery in dogs with spinal cord injury (SCI) secondary to intervertebral disc herniation (IVDH). Hypothesis: Magnetization transfer ratio (MTR), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), and fractional anisotropy (FA) will be significantly different in patients with a successful outcome compared to patients with an unsuccessful outcome. Animals: 61 dogs with SCI secondary to IVDH were included in the final analysis. All dogs had to undergo surgical correction for SCI secondary to IVDH and be followed out for 12 weeks. Methods: Prospective cohort study. MTR, MD, AD, RD, and FA were calculated in dogs with SCI secondary to IVDH. A Wilcoxon signed-rank test was used to compare MTR, MD, AD, RD, and FA values between patients with a successful outcome and patients with an unsuccessful outcome. Statistical significance was set at p<0.05. For quantitative imaging surrogates with a significant relationship with outcome, a receiver operator characteristic (ROC) curve analysis was performed and the sensitivity and specificity for predicting successful outcome. Results: MTR (p=0.0013) was significantly lower in patients with a successful outcome compared to patients with an unsuccessful outcome. FA (p=0.435) was not significantly between groups. MD (p=0.0006), AD (p=0.0008) and RD (p=0.0002) were significantly higher in patients with a successful outcome compared to patients with an unsuccessful outcome. ROC curves were performed for MTR, AD and RD. If MTR was ≤ 53, AD ≥ 1.7 × 10-3mm2/s or RD ≥ 0.37 × 10-3 mm2/s, this resulted in a sensitivity of 96.3% and specificity of 100 in predicting a successful outcome. Conclusion and clinical relevance: MTR, MD, AD, and RD were helpful in predicting successful outcome in canine patients with surgically treated SCI secondary to IVDH. A larger cohort is needed for further evaluation. / Master of Science / Background: Certain magnetic resonance imaging (MRI) techniques can provide information about the severity of spinal cord injury. The information obtained from these MRI techniques can be helpful in predicting prognosis in dogs with intervertebral disc disease (IVDD). Hypothesis: We hypothesized that the measurements obtained from these MRI techniques would be able to predict the patients who would be able to walk following surgery (good long-term outcome), versus the patients who did not regain the ability to walk following surgery (poor long-term outcome). Animals: 62 MRIs were performed on dogs with IVDD in our study and were followed out for 12 weeks following surgery to assess long-term outcome. Results: Of the 5 MRI techniques investigated, 4 of the techniques were found to be helpful in predicted long-term outcome. When these techniques were combined, the ability to predict long-term outcome improved. Using the combined technique, all 53 patients predicted to have a good long-term had a good long-term outcome. For patients with a poor long-term outcome, 9 were predicted to have a poor long-term outcome, but only 7 patients had a poor long-term outcome. Conclusion and clinical relevance: MRI can be helpful in predicting long-term outcome in dogs with IVDD following surgery. A larger population of dogs is needed for further evaluation.

Fully differentiated muscle fibers can undergo considerable phenotypic changes in order to adjust to changing conditions of the physiological environment. It is generally accepted that the electrical impulses a muscle receives play a role in modulating the quantities of metabolic proteins (glycolytic and oxidative enzymes) and types of contractile proteins (myosin heavy chain, MHC) that are expressed. Research has shown that decreased neuromuscular activation following spinal cord transection (ST) results in adaptations in the physiological characteristics of paralyzed muscles, including atrophy and an accompanying loss of force production, and transformations of contractile and metabolic proteins toward a more fatigable state. However, it remains unclear whether or not a strong interdependence of energy metabolism and MHC isoform composition persists. Therefore, the goal of this study was to identify and quantify relative myosin heavy chain (MHC) isoform expression and metabolic enzyme profile adaptations at multiple time points (1, 3 and 6 months) in soleus fibers of rats following spinal cord transection (ST). To accomplish this, female Sprague-Dawley rats (~150 g, n = 15) were subjected to complete transection of the spinal cord at a mid-thoracic level. Age and weight-matched, non-operated rats served as controls (n = 15). The soleus was processed for quantitative single fiber histochemical analyses for succinate dehydrogenase (SDH, oxidative marker) and a-glycerophosphate dehydrogenase (GPD, glycolytic marker) activities (~30 fibers/muscle) and immunohistochemical analysis for MHC isoform composition. The total number of soleus fibers analyzed was ~900. Oxidative capacity was increased in muscle fibers at all time points after ST. Specifically, SDH activity was significantly higher than controls by 142, 127 and 206% at 1, 3 and 6 months post-ST, respectively. ISDH, a measure of total oxidative power, also increased in muscle fibers at all time points after ST. For example, 6 months after ST ISDH activity was 93% higher than controls (91.8-3.8 vs. 47.6-0.9 OD x 10-3, respectively). Glycolytic capacity peaked one month after ST. Thereafter, glycolytic capacity of all fibers steadily declined. For example, by 6 months, GPD activity had declined by 76% compared to 1 month GPD activities (3.3-0.2 vs. 13.7-1.4 OD x 10-3, respectively). These data suggest that the increases in glycolytic capacity are transient as fibers transition toward a faster MHC phenotype and then return towards control levels as fibers of a given type become phenotypically stable. The GPD/SDH ratio, an index of metabolic substrate utilization, peaked at one month after ST (394-41) and significantly decreased at 3 months (224-10) and at 6 months (95-7) after ST. Therefore, a shift occurred such that a greater dependence on oxidative metabolism was apparent. These data suggest that the oxidative capacities of soleus muscle fibers are not compromised after ST. In fact, as the fibers transitioned toward faster MHC isoforms, the GPD/SDH ratio was maintained or decreased, suggesting a reliance on oxidative metabolism regardless of MHC isoform composition. This might imply a dissociation between the contractile and metabolic characteristics of paralyzed soleus muscle fibers. However, these data are consistent with previous data and suggest that the increased fatigability observed after chronic reductions in neuromuscular activity are not due to compromised capacities for ATP synthesis. / Master of Science

Spontaneous activity in neuronal networks in vitro is common and has been well documented. However, alteration of spontaneous activity in such networks via conditioning electrical stimulation has received much less experimental attention. Two different patterns of electrical stimulation were used to enhance or depress the level of spontaneous activity in spinal cord cultures. High-frequency stimulation (HFS), a method routinely shown to increase the efficacy of synaptic transmission, was employed to augment spontaneous activity. Low-frequency stimulation (LFS), the technique often applied to depress synaptic efficacy, was employed to decrease spontaneous activity. In addition, LFS was used to reverse the effect of HFS on spontaneous activity. Likewise, HFS was applied to counter the effect of LFS. Because these networks were grown on multi-microelectrode plates (MMEPs), this allowed the simultaneous stimulation of any combination of the 64 electrodes in the array. Thus, the possible differences in response to single versus multi-electrode stimulation were also addressed. Finally, test-pulses were delivered before and after the conditioning stimulation on the same stimulation electrode(s) in order to assess the change in mean evoked action potentials (MEAPs). Dissociated spinal tissue from embryonic mice was allowed to mature into self-organized networks that exhibited spontaneous bursting activity after two weeks of incubation. Spontaneous activity was monitored from up to 14 recording channels simultaneously. Although uniform responses to stimulation across all recording electrodes were rarely observed, a large majority of the recording channels had similar responses. Spontaneous activity was increased in 52% of 89 HFS trials, whereas activity was decreased in 35% of 75 LFS trials. The duration of most of these increases was less than 5 minutes. When there were substantial and long-term (> 15 min) changes in spontaneous activity, the opposing stimulation pattern successfully reversed the effect of the previous stimulation. The percent change in MEAPs following conditioning stimulation suggested that synaptic modification had taken place in 75% of all test-pulse stimulation trials.

Rapid receptive field (RF) reorganization of somatosensory neurons in the rat dorsal horn was examined using extracellular single unit recording. Subcutaneous injection of lidocaine into RFs of dorsal horn neurons results in expansion of their RFs within minutes. The expanded RFs appear adjacent to or/and proximal to original RFs. Out of 63 neurons tested, 36 (58%) show RF reorganization. The data suggest that dorsal horn of spinal cord is one of the initial sites for RF reorganization. The neural mechanisms of this effect are not well understood. We propose that changes in biophysical properties (membrane conductance, length constant) of the neurons resulting from lidocaine injection contribute to RF reorganization. Iontophoretic application of glutamate onto dorsal horn neurons that show lidocaine induced RF's expansion were used to test the model. Application of glutamate produced reduction of reorganized RFs in 9 of 20 (45%) tested cells. Application of NBQX produced no effect on either original or expanded RFs indicate that RF shrinkage effects of glutamate involve NMDA receptors. The results are consistent with the prediction of the proposed model. Subcutaneous injection of capsaicin into tactile RFs of low threshold mechanoreceptive dorsal horn neurons produced no effect on the RF sizes that are consistent with other studies. Following the injection, the original RFs were completely silenced (46%) or remained responsive (54%).

Spinal cord injury (SCI) is a devastating disease which poses health problems in human and veterinary medicine. SCI causes neurological disability, with loss of motor, sensory and autonomic function. This study investigated the efficacy of local treatment with IKVAV-peptide on spinal cord regeneration following compression injury at T12 vertebra in Balb-c mice. IKVAV-peptide is a membrane spanning peptide known to have a long half-life and the peptide motif IKVAV. Thirty Blab-c female mice were used. Hemilaminectomy was performed at T12 and spinal cords were compressed using extradural application of a 24 g modified aneurysm clip for 1 min in the treatment groups. After 24 hours mice were treated with one of 4 different treatments including isoleucine-lysine-valine-alanine-valaine(IKVAV), IKVAVpeptide, peptide and mannitol (vehicle). Functional improvement was assessed every day using Basso, Beattie, Bresnahan (BBB) Locomotor Rating Scale. 28 days later, the mice were euthanized, and spinal cord segments were studied histologically. Statistical analysis, one-way and two-way analysis of variance (ANOVA) and linear regression model were used to measure some parameters and describe the outcome after SCI. Over a 4weeks period, IKVAV-peptide group demonstrated statistical and histological evidence of cellular reconstruction and behavioral improvement. The BBB score in the IKVAV-peptide group increased by 5.4 (25%) points, the IKVAV and peptide groups by approximately 1 point (5%) and the mannitol group by 4 points (19%). The number of protoplasmic astrocytes in the IKVAV-peptide group was significantly increased compared to IKVAV, mannitol and normal groups but not with the peptide group (p<0.001). Neuron and muscle bundle size were also increased significantly (p<0.05 and p<0.007, resp.) in the IKVAV-peptide group compared to other treatment groups. The treated control groups showed cellular and gross damages including neuron inactivation and muscle atrophy, gliosis and inability of movement. / Graduation date: 2013