Multiple and early hyperbaric oxygen treatments enhance muscle healing after muscle contusion injury: a pilot study.

BACKGROUND: The optimal timing of hyperbaric oxygen (HBO2) treatments for the best recovery following muscle injury has yet to be determined. Thus, the optimal number and timing of HBO2 treatments for maximal muscle regeneration were explored. METHODS: The HBO2 treatment protocol consisted of 2.5 ATA 100% oxygen for 120 minutes. Muscle-injured rats were randomized to one of 10 groups: single HBO2 treatment immediately after injury (HBO 1T day 0), one day (HBO 1T day 1), three days (HBO 1T day 3) and five days (HBO 1T day 5) after injury; three HBO2 treatments from immediately after injury to two days after injury (HBO 3T day 0-2), from one to three days after injury (HBO 3T day 1-3), from three to five days after injury (HBO 3T day 3-5), from five to seven days after injury (HBO 3T day 5-7); five daily HBO2 treatments (HBO 5T); and no treatment (NT). RESULTS: HBO 5T and HBO 3T day 0-2, days 1-3 and days 3-5 significantly promoted CD206-positive cell infiltration, satellite cell differentiation and muscle regeneration compared to the NT group. CONCLUSION: Five HBO2 treatments and three HBO2 treatments within three days of injury promote muscle regeneration.

The influence of hyperbaric environment on the skeletal muscle mitochondrial energetic of rats after induced muscle contusion.

OBJECTIVE: Analyze the influence of the hyperbaric environment on skeletal muscle mitochondrial bioenergetic end-points of rats submitted to muscle contusion. METHODS: Twelve female Wistar rats were randomly assigned to three groups. All rats were submitted to muscle contusion in the right gastrocnemius through a standard protocol. The control group (C) remained under normobaric conditions without any treatment. The hyperbaric air (HB) and the hyperbaric oxygen (HBO2) groups had four sessions of HBO2 therapy 60 minutes, six, 12, 24 and 48 hours after the injury at 253.25 kPa (2.5 atmospheres absolute/ATA) with air or 100% oxygen, respectively. The animals were sacrificed 48 hours after muscle injury, and both muscles (injured and non-injured) were analyzed. Muscle mitochondrial bioenergetics and mitochondrial permeability transition pore (MPTP) susceptibility were evaluated. RESULTS: Significant differences were found in all parameters between the injured and the non-injured gastrocnemius in the C group. In the HB group, significantly better results concerning bioenergetics-related end points with complex I and II substrates where found in the right gastrocnemius, whereas in the HBO2 group the time to Vmax (time that elapsed until the faster swelling kinetics starts) was significantly higher and the swelling amplitude was significantly smaller than in other groups, which suggest a lower susceptibility to MPTP opening. CONCLUSION: The present data suggest that hyperbaric exposure, particularly with oxygen, positively modulates the efficiency of skeletal muscle mitochondria after muscle contusion.

Effects of electroacupuncture on recovery of the electrophysiological properties of the rabbit gastrocnemius after contusion: an in vivo animal study.

BACKGROUND: Our preliminary studies indicated that electroacupuncture (EA) at the ST36 and Ashi acupoints could promote regeneration of the rabbit gastrocnemius (GM) by improving microcirculation perfusion, promoting the recovery of myofiber structures, and inhibiting excessive fibrosis. However, the effects of EA on recovery of the electrophysiological properties of the GM after contusion are not yet clear. Thus, the purpose of this study was to investigate the effects of EA at the Zusanli (ST36) and Ashi acupoints with regard to recovery of the electrophysiological properties of the rabbit GM after contusion. METHODS: Forty-five rabbits were randomly divided into three groups: normal, contusion, and EA. After an acute GM contusion was produced (in rabbits in the contusion and EA groups), rabbits in the EA group were treated with electrostimulation at the ST36 and Ashi acupoints with 0.4 mA (2 Hz) for 15 min. The contusion group received no EA treatment. At different time points (7, 14, and 28 days) after contusion, we performed surface electromyography (EMG) and measured the nerve conduction velocity (NCV) of the GM and the GM branch of the tibial nerve. We also examined acetylcholinesterase (AchE) and Agrin expression in the neuromuscular junction (NMJ) via immunohistochemistry. RESULTS: Compared with the contusion group, the EMG amplitude and NCV in rabbits in the EA group were significantly higher at all time points after contusion. AchE and Agrin expression in the EA group were significantly higher than those in the contusion group. CONCLUSIONS: Our results showed that EA at the ST36 and Ashi acupoints effectively promoted recovery of the electrophysiological properties of the rabbit GM after contusion. The effects of EA were realized by promotion of the regeneration of myofibers and nerve fibers, as well as acceleration of NMJ reconstruction by upregulation of AchE and Agrin expression in the motor endplate area.

Hyperbaric oxygen therapy treatment for the recovery of muscle injury induced in rats.

INTRODUCTION: We evaluated the effect of hyperbaric oxygen treatment (HBOT) in the recovery of muscle injury in rats. MATERIALS AND METHODS: Twelve female Wistar rats, weighing 200-250 g, were submitted to contusion of the right gastrocnemius muscle. Animals were then randomly assigned to an untreated control group or an HBOT-treated group. The HBOT group was given three, 60-minute sessions of HBOT at 253 kPa pressure at 24, 48 and 72 hours post injury. After the last session all animals were sacrificed and both gastrocnemius muscles removed, the left muscle as an internal control. Blood samples were taken for creatine phosphokinase (CPK). Using a standard traction technique, the muscles were analysed for their biomechanical properties: hardness, maximum elongation and maximum weight. RESULTS: Significant differences were found between uninjured and injured muscles and between untreated and HBOT groups in maximum weight and hardness: maximum weight in the non-treated group 18.27 ± 2.99 N versus 26.18 ± 2.84 N in the HBOT group (P = 0.007); hardness in the non-treated group 2.24 ± 0.38 103 N m⁻¹ versus 3.19 ± 0.32 10³ N m⁻¹ in the HBOT group (P = 0.001). The difference in maximum elongation was not significant (P = 0.793). CPK was significantly different between the two groups (non-treated 6,445 ± 387 i.u. L⁻¹; HBOT 4,551 ± 80 i.u. L⁻¹; P = 0.009). CONCLUSIONS: HBOT seems to play a positive role in the recovery of induced muscle injury in rats. However relevant, these results cannot be extrapolated to humans, for whom further clinical studies are warranted.

An experimental study of chest compression during chiropractic manipulation of the thoracic spine using an anthropomorphic test device.

PURPOSE: Chiropractic manipulation of the thoracic spine may induce chest deformations in the anterior-posterior direction. Yet, few studies have examined the biomechanical response of the chest associated with these manipulations. Consequently, an experimental analysis was undertaken to quantify chest compressions resulting from chiropractic thoracic spine manipulations and to estimate amount of risk for injury. METHODS: A 2-part study approach was used with a Hybrid III anthropomorphic test dummy. In part 1, the dummy was positioned prone on a chiropractic table and subjected to thoracic spine manipulation by 2 experienced doctors of chiropractic. Chest compressions were quantified in the anterior-posterior direction. Manipulation forces were self-selected, with "typical" and "maximum" efforts examined. In part 2, the dummy was positioned beneath a force-instrumented mechanical piston device. Using the piston, chest compressions were induced with magnitudes identical to those recorded during chiropractic manipulation as well as magnitudes sufficient to induce injury. In all trials, force measurements were recorded. RESULTS: Thoracic manipulations incorporating the typical and maximum efforts by the chiropractors resulted in maximum chest compressions attaining 1.8% and 4.5% of total chest depth, respectively. According to previously developed correlations between chest compression and injury severity defined using the Abbreviated Injury Scale (AIS), maximum chest compression measured during this study was only 22.7% of the compression required for greater than 10% risk of an AIS 1 injury. Abbreviated Injury Scale 1 level injuries are graded as minor severity and correspond to sternum contusion or fracture of a single rib. CONCLUSIONS: Results from this preliminary study showed that maximum chest compression during thoracic spine manipulation corresponded to minimal risk of AIS 1 level injuries.

810 nm Wavelength light: an effective therapy for transected or contused rat spinal cord.

BACKGROUND AND OBJECTIVES: Light therapy has biomodulatory effects on central and peripheral nervous tissue. Spinal cord injury (SCI) is a severe central nervous system trauma with no effective restorative therapies. The effectiveness of light therapy on SCI caused by different types of trauma was determined. STUDY DESIGN/MATERIALS AND METHODS: Two SCI models were used: a contusion model and a dorsal hemisection model. Light (810 nm) was applied transcutaneously at the lesion site immediately after injury and daily for 14 consecutive days. A laser diode with an output power of 150 mW was used for the treatment. The daily dosage at the surface of the skin overlying the lesion site was 1,589 J/cm(2) (0.3 cm(2) spot area, 2,997 seconds). Mini-ruby was used to label corticospinal tract axons, which were counted and measured from the lesion site distally. Functional recovery was assessed by footprint test for the hemisection model and open-field test for the contusion model. Rats were euthanized 3 weeks after injury. RESULTS: The average length of axonal re-growth in the rats in the light treatment (LT) groups with the hemisection (6.89+/-0.96 mm) and contusion (7.04+/-0.76 mm) injuries was significantly longer than the comparable untreated control groups (3.66+/-0.26 mm, hemisection; 2.89+/-0.84 mm, contusion). The total axon number in the LT groups was significantly higher compared to the untreated groups for both injury models (P<0.05). For the hemisection model, the LT group had a statistically significant lower angle of rotation (P<0.05) compared to the controls. For contusion model, there was a statistically significant functional recovery (P<0.05) in the LT group compared to untreated control. CONCLUSIONS: Light therapy applied non-invasively promotes axonal regeneration and functional recovery in acute SCI caused by different types of trauma. These results suggest that light is a promising therapy for human SCI.

Cupping: from a biomechanical perspective.

The effectiveness of the cupping technique, a treatment modality in Traditional Chinese Medicine, in stimulating acupuncture points for pain relief was examined in this paper from a biomechanical perspective. Parametric studies including the effects of vacuum pressure, loading rate, friction coefficient at the cup-skin interface, and size and shape of the cup were carried out using a model based on the finite-element method. The anatomical structures of skin, fat, and muscle were modelled. All the soft-tissue layers were assumed to be nonlinearly elastic and viscoelastic. The rim of the cup was also modelled to study the interaction between cup and skin; the cup rim was assumed to be rigid. The simulation results showed that the stresses in the soft tissue were increased for increasing applied vacuum pressures and that the effects of cupping were mostly limited to the region enclosed by the cup. The simulations also indicated that the magnitude of the applied vacuum may have had direct implications for the severity of bruising of the skin following cupping treatment. Most significantly, the simulation results contradicted the established practice of cup size selection according to the depth of the disorder. Experimental verification of the proposed multi-layered finite-element model is presented. The nature of the bruising inherent to the cupping treatment is also explained by the proposed model.

Chronic spinal cord injury induced changes in the responses of thalamic neurons.

Sensory disturbances following spinal cord injury (SCI) include chronic pain, which is often localized at spinal levels just rostral to the lesion (referred to as at-level neuropathic pain) and not effectively relieved by traditional treatments. In the present study, a clinically relevant spinal contusion injury was made at the spinal T8 level in 11 deeply anesthetized male rats. Behavioral testing just prior to terminal electrophysiological experiments (done at 30 days post-injury) demonstrated at-level sensitivity to touching the trunk (i.e., allodynia) in 64% of the animals. Electrophysiological data (urethane anesthesia) were obtained for 218 single somatovisceral convergent neurons that were located throughout 12 subregions of the thalamus. In total, 90% (197 of 218) responded to noxious at-level pinch, compared to 52% for pinching the dorsal trunk at the same level in uninjured controls (our previously published data--recorded from 133 total neurons). In addition, 33% of the total neurons tested also responded to gentle touch (dorsal trunk) versus 9% in controls. A comparison of electrophysiological and behavioral data for each individual animal reveals novel tactile neuronal responses within ventral and posterior thalamic subnuclei for those rats showing signs of at-level allodynia. These data suggest that neurons in specific regions of thalamus undergo significant changes in responsiveness following severe chronic SCI. The observed plasticity and ensuing hypersensitivity are likely part of the central reorganization producing the multitude of sensory disturbances that surface following SCI.

Cardiopulmonary function after pulmonary contusion and partial liquid ventilation.

PURPOSE: To compare the effects of mechanical ventilation with either positive end-expiratory pressure (PEEP) or partial liquid ventilation (PLV) on cardiopulmonary function after severe pulmonary contusion. METHODS: Mongrel pigs (32 +/- 1 kg) were anesthetized, paralyzed, and mechanically ventilated (8-10 mL/kg tidal volume; 12 breaths/min; FiO2 = 0.5). Systemic hemodynamics and pulmonary function were measured for 7 hours after a captive bolt gun delivered a blunt injury to the right chest. After 5 hours, FiO2 was increased to 1.0 and either PEEP (n = 7) in titrated increments to 25 cm H2O or PLV with perflubron (LiquiVent, 30 mL/kg, endotracheal) and no PEEP (n = 7) was administered for 2 hours. Two control groups received injury without treatment (n = 6) or no injury with PLV (n = 3). Fluids were liberalized with PEEP versus PLV (27 +/- 3 vs. 18 +/- 2 mL.kg-1.h-1) to maintain cardiac filling pressures. RESULTS: Before treatment at 5 hours after injury, physiologic dead space fraction (30 +/- 4%), pulmonary vascular resistance (224 +/- 20% of baseline), and airway resistance (437 +/- 110% of baseline) were all increased (p < 0.05). In addition, PaO2/FiO2 had decreased to 112 +/- 18 mm Hg, compliance was depressed to 11 +/- 1 mL/cm H2O (36 +/- 3% of baseline), and shunt fraction was increased to 22 +/- 4% (all p < 0.05). Blood pressure and cardiac index remained stable relative to baseline, but stroke index and systemic oxygen delivery were depressed by 15 to 30% (both p < 0.05). After 2 hours of treatment with PEEP versus PLV, PO2/FiO2 was higher (427 +/- 20 vs. 263 +/- 37) and dead space ventilation was lower (4 +/- 3 vs. 28 +/- 7%) (both p < 0.05), whereas compliance tended to be higher (26 +/- 2 vs. 20 +/- 2) and shunt fraction tended to be lower (0 +/- 0 vs. 7 +/- 4). With PEEP versus PLV, however, cardiac index, stroke index, and systemic oxygen delivery were 30 to 60% lower (all p < 0.05). Furthermore, although contused lungs showed similar damage with either treatment, the secondary injury in the contralateral lung (as manifested by intra-alveolar hemorrhage) was more severe with PEEP than with PLV. CONCLUSIONS: Both PEEP and PLV improved pulmonary function after severe unilateral pulmonary contusion, but negative hemodynamic and histologic changes were associated with PEEP and not with PLV. These data suggest that PLV is a promising novel ventilatory strategy for unilateral pulmonary contusion that might ameliorate secondary injury in the contralateral uninjured lung.

Synaptic remodeling and free radical formation after brain contusion injury in the rat.

The purpose of this study was to explore whether bilateral frontal cortex contusion in rats would demonstrate changes relevant for understanding the pathology of frontal lobe injury in humans. Rats were allowed to survive for 3, 7, or 18 days postinjury (dpi). In the contused rats, albumin was trapped in frontal cortices, as well as in other brain areas, showing that neurons were exposed to plasma components. In the sham-operated rats, which had only craniotomy but no penetration of dura, the level of trapped albumin was also increased compared to intact controls, suggesting a partial lesion-like condition. Choline acetyltransferase activity was severely decreased in the frontal cortices of contused rats, compared to the sham-operated controls. The decrease was most pronounced at 3 dpi and less pronounced 18 dpi, suggesting that after the initial damage, regeneration of the cholinergic terminals occurred. The concentration of the mature presynaptic membrane protein D3(SNAP-25) was also decreased in the frontal cortices of contused rats at 3 and 7 dpi, whereas it was normalized at 18 dpi. Previously, we have evaluated changes in the rate of synaptic remodeling in brain injury by calculating the ratio of the neural cell adhesion molecule (NCAM) to D3(SNAP-25). The NCAM/D3(SNAP-25) ratio at 3 dpi was elevated by more than 60% in the frontal cortices of contused rats, suggesting a high initial rate of synaptic remodeling. The ratios were smaller at 7 and 18 dpi, suggesting that after the initial burst, the rate of remodeling leveled off. In contrast, astrocyte activation was less pronounced at 3 dpi than at 7 and 18 dpi, as measured by the levels of glial fibrillary acidic protein and glutamine synthetase immunoactivities. The immunoreactivity of glutamine synthetase more than doubled in the contused brains but its enzymatic activity increased less than 50%, suggesting that many enzymatic centers had been inactivated by free radicals. Calculated as the difference between the relative immunoreactivity and the relative enzymatic activity the "lost glutamine synthetase activity" increased continuously in frontal cortex and striatum from 3 to 18 dpi, indicating the production of free radicals long after the initial contusion event. In conclusion, following frontal cortical contusions the early synaptic damage was partly compensated by synaptic remodeling. We suggest that the continuous production of free radicals may have contributed to the declining remodeling rate and impair functional recovery.

The effect of exercise on the presence of leukocytes, erythrocytes and collagen fibers in skeletal muscle after contusion.

OBJECTIVE: To determine the comparative rate of resolution of a contusion resulting from mechanical trauma to skeletal muscle, as a function of one of four exercise regimens. DESIGN: Randomized control trial. The four exercise regimens were: running with its onset immediately after injury, running with a 72 hr delay after injury, swimming with immediate onset, or swimming with a 72 hr delay. Control did not exercise. SETTING: Small-animal laboratory. PARTICIPANTS: Male Sprague-Dawley rats. INTERVENTION: A small animal traumatizing machine applied to the biceps femoris. MAIN OUTCOME MEASURES: The rate of contusion resolution was determined by a manual count of erythrocytes, leukocytes and collagen fibers in the contusion, and the data were analyzed using analysis of variance. RESULTS: Exercise of any type produced a greater decline in erythrocyte count (28.2% after 32 days vs. control) than no exercise. Immediate onset of any of the exercise regimens after injury resulted in a greater decline in erythrocyte count (32.7% after 32 days vs. control) and in leukocyte count (17.3% after 32 days vs. control) than delayed onset. Running with either immediate or delayed onset of exercise after injury produced a greater decline in erythrocyte count (36.2% after 32 days vs. control) than swimming. Running with its onset immediately after injury produced the greatest overall rate of decrease in erythrocyte count (44.8% after 32 days vs. control), and the second greatest overall rate of decrease in leukocyte count (15.0% after 32 days vs. control). CONCLUSIONS: Running with immediate onset is the regimen of choice. Any of the given exercises is preferable to no exercise, immediate onset of exercise is preferable to delayed onset, and running is preferable to swimming.

Electrical field distribution within the injured cat spinal cord: injury potentials and field distribution.

This study investigated the spontaneous injury potentials measured after contusion or transection injury to the cat spinal cord. In addition, the distribution of electrical field potentials on the surface and within the spinal cord were measured following applied electrical fields after transection and contusion injuries. After transection of the spinal cord, the injury potentials were -19.8 +/- 2.6 mV; after contusion of the spinal cord, the injury potentials were -9.5 +/- 2.2 mV. These potentials returned to control values within 2.5-4h after injury. The electrical field distribution measured on the dorsal surface, as well as within the spinal cord, after the application of a 10 microA current, showed little difference between contusion and transection injuries. Scalar potential fields were measured using two configurations of stimulating electrodes: dorsal to dorsal (D-D), in which both electrodes were placed epidurally on the dorsal surface of the spinal cord, and ventral to dorsal (V-D), in which one electrode was placed dorsally and one ventrally. As reported in normal uninjured cats, the total current in the midsagittal plane for the D-D configuration was largely confined to the dorsal portion of the spinal cord; with the V-D configuration, the current distribution was uniform throughout the spinal cord. In the injured spinal cord, the equipotential lines midway between the stimulating electrodes have a wider separation than in the uninjured spinal cord. Because the magnitude of the electrical field E is equal to the current density J multiplied by the resistivity r, this suggests that either the current density is reduced or that the resistivity is reduced.

Myoelectric evoked potentials versus locomotor recovery in chronic spinal cord injured rats.

The purpose of this study was to determine the utility of descending evoked potentials in evaluating functional recovery in rats after spinal cord contusion injury. Rats received thoracic contusions at T9 using a controlled-displacement impactor. They were evaluated for 5 weeks postinjury using auditory startle responses (ASR) while alert, or by cerebellar motor evoked potentials (CMEP) while anesthetized. ASR and CMEP were recorded electromyographically from forelimb and hindlimb muscles. Open field locomotor performance was also assessed and recovered to almost normal levels by 3 weeks postinjury. Histologic analysis of the injury site indicated that the contusions destroyed approximately 70% of the cross-sectional area of the cord. Although the remaining 30% was sufficient to preserve nearly normal locomotor behavior, ASR and CMEP amplitudes in hindlimb flexors and extensors were reduced by 90% or more after injury and showed virtually no recovery. Significant ASR and CMEP responses were present in the cutaneous trunk muscles of the lower torso after injury. These muscles are innervated via peripheral nerves originating at cord levels above the injury. Multi-wave field potentials normally recorded from the dorsal cord surface in response to cerebellar stimulation were absent in injured rats, suggesting minimal if any activation of segmental neurons via the pathways normally mediating CMEP. The tracts mediating ASR and CMEP thus appear to be highly sensitive to mild spinal cord trauma but are evidently not essential for support or walking.