Effects of different vibration frequencies on spinal cord reflex circuits and thermoalgesic perception

Objectives:We studied the effect of different vibration frequencies on spinal cord excitability and heat pain perception. We hypothesized that the effects of vibration on spinal cord reflexes, and, also those on heat pain perception, depend on vibration frequency.Methods:In 9 healthy subjects, we applied vibration over the tibialis anterior muscle at three different frequencies (50, 150, or 250 Hz) on spinal cord reflex excitably, tested with the H reflex and the T wave in the soleus muscle, as well as on sensory and pain perception, tested by measuring warm perception (WT) and heat pain perception thresholds, (HPT) in sites rostral and caudal to vibration. Exams were carried out before, during, and after vibration.Results:The amplitude of the H reflex and T wave significantly decreased during vibration in comparison to baseline. Low frequencies (50 and 150Hz) induced greater reflex suppression than high frequency (250Hz). No significant changes were observed on WT and HPT.Conclusions:The effects of vibratory stimulation can be summarized as frequency-related suppression of the spinal cord excitability without an effect on warm and heat pain perception. The present results may help to design vibration-related interventions intended to diminish spinal cord reflex excitability in spastic patients.     

Single session exercises and concurrent functional electrical stimulation are more effective on muscles’ force generation than only exercises in spinal cord injured persons: a feasibility study

Objectives:To evaluate impact of first therapy session, containing functional electrical stimulation (FES) and therapeutic exercises (TE) on erector spinae (ES) and rectus abdominis (RA) force generation in persons with spinal cord injury (SCI).Methods:Five men with SCI were divided in two groups - FES+TE received concurrent FES on ES and RA and TE, TE only TE. Participants performed exercises for improving sitting balance and posture. Muscles’ electrical activity was evaluated by electromyography; amplitude (AEMG) and median frequency (MF) were used for analysis.Results:AEMG of ES left (L) increased 292.9% (g=-0.92), right (R) 175% (g=-1.01), RA L 314.3% (g=-0,81, P<0.05), R 266.7% (g=-0.08) in FES+TE. AEMG of ES L increased 47.6% (g=-0.46), R 96.4% (g=-0.95); RA L 7.1% (g=-0.97), but R decreased 6.7% (g=0.12) in TE. MF of ES L increased 108.5% (g=-0.74), R 184% (g=-1.25); RA L 886.7% (g=3-05, P<0.05), R 817.6% (g=-2.55, P<0.05) in FES+TE. MF of ES L increased 95.2% (g=-1.02), R 161.4% (g=-1.64); RA L 3,2% (g=-0.06), R 30.8% (g=-0.46) in TE.Conclusions:In SCI persons, single session exercises and concurrent functional electrical stimulation may be more effective on muscles` force generation than only exercises. However, replication of the results is needed before clinical implementation.     

A single pair of interneurons controls motor neuron activity during pre-ecdysis compression behavior in larval Manduca sexta

Manduca sexta molts several times as a larva (caterpillar) before becoming a pupa and then an adult moth. Each molt culminates in ecdysis behavior, during which the old cuticle is shed. Prior to each larval ecdysis, the old cuticle is loosened by pre-ecdysis behavior, which includes rhythmic, synchronous compressions of the abdomen. A previous study indicated that motor neuron activity during pre-ecdysis compression behavior is driven by an ascending neural pathway from the terminal abdominal ganglion. The present study describes a pair of interneurons, designated IN-402, that are located in the terminal ganglion and belong to the ascending pathway. Each IN-402 is synchronously active with pre-ecdysis compression motor bursts, and bilaterally excites compression motor neurons throughout the abdominal nerve cord via apparently monosynaptic connections. The pair of IN-402s appears to be the sole source of rhythmic synaptic drive to the motor neurons during the pre-ecdysis compression motor pattern. These interneurons play a key role in the production of larval pre-ecdysis behavior, and are candidates for contributing to the developmental weakening of pre-ecdysis behavior at pupation.Abbreviations A3, A4... abdominal ganglion 3, abdominal ganglion 4... - AT terminal abdominal ganglion - DN _A anterior branch of the dorsal nerve - EH eclosion hormone - EPSP excitatory postsynaptic potential     

Gravitational force modulates muscle activity during mechanical oscillation of the tibia in humans

Mechanical oscillation (vibration) is an osteogenic stimulus for bone in animal models and may hold promise as an anti-osteoporosis measure in humans with spinal cord injury (SCI). However, the level of reflex induced muscle contractions associated with various loads (g force) during limb segment oscillation is uncertain. The purpose of this study was to determine whether certain gravitational loads (g forces) at a fixed oscillation frequency (30 Hz) increases muscle reflex activity in individuals with and without SCI. Nine healthy subjects and two individuals with SCI sat with their hip and knee joints at 90° and the foot secured on an oscillation platform. Vertical mechanical oscillations were introduced at 0.3, 0.6, 1.2, 3 and 5g force for 20 s at 30 Hz. Non-SCI subjects received the oscillation with and without a 5% MVC background contraction. Peak soleus and tibialis anterior (TA) EMG were normalized to M-max. Soleus and TA EMG were <2.5% of M-max in both SCI and non-SCI subjects. The greatest EMG occurred at the highest acceleration (5g). Low magnitude mechanical oscillation, shown to enhance bone anabolism in animal models, did not elicit high levels of reflex muscle activity in individuals with and without SCI. These findings support the g force modulated background muscle activity during fixed frequency vibration. The magnitude of muscle activity was low and likely does not influence the load during fixed frequency oscillation of the tibia.     

The role of Slit-Robo signaling in the generation, migration and morphological differentiation of cortical interneurons

Cortical interneurons in rodents are generated in the ventral telencephalon and migrate tangentially into the cortex. This process requires the coordinated action of many intrinsic and extrinsic factors. Here we show that Robo1 and Robo2 receptor proteins are dynamically expressed throughout the period of corticogenesis and colocalize with interneuronal markers, suggesting that they play a role in the migration of these cells. Analysis of Robo mutants showed a marked increase in the number of interneurons in the cortices of Robo1^−/−, but not Robo2^−/−, animals throughout the period of corticogenesis and in adulthood; this excess number of interneurons was observed in all layers of the developing cortex. Using BrdU incorporation in dissociated cell cultures and phosphohistone-3 labeling in vivo, we demonstrated that the increased number of interneurons in Robo1^−/− mice is, at least in part, due to increased proliferation. Interestingly, a similar increase in proliferation was observed in Slit1^−/−/Slit2^−/− mutant mice, suggesting that cell division is influenced by Slit-Robo signaling mechanisms. Morphometric analysis of migrating interneurons in Robo1^−/−, Robo2^−/− and Slit1^−/−/Slit2^−/−, but not in Slit1^−/− mice, showed a differential increase in neuronal process length and branching suggesting that Slit-Robo signaling also plays an important role in the morphological differentiation of these neurons.     

Mandibular premotor interneurons of larval Manduca sexta

Simultaneous intracellular recordings were made from interneurons and from closer or opener mandibular motor neurons in the isolated suboesophageal ganglion of the larva of Manduca sexta. This article describes various morphologically and physiologically distinguishable premotor spiking interneurons which make direct excitatory connections with the motor neurons. In addition, two presumptive non-spiking interneurons make excitatory and inhibitory connections respectively with opener motor neurons. Both classes of interneurons receive excitatory and inhibitory sensory inputs from the mouthparts. Their circuitry and functions are discussed.Abbreviations A anterior - AP action potential - CEC circumoesophageal connective - Cl-MN closer motor neuron - EPSP excitatory postsynaptic potential - IN interneuron - IPSP inhibitory postsynaptic potential - MdN mandibular nerve - MN motor neuron - MxN maxillary nerve - O-MN opener motor neuron - PSP postsynaptic potential     

An electron microscopic study of macroglia and microglia in the lateral funiculus of the developing spinal cord in the fetal monkey

Summary An electron-microscopic study has been made of the glial cells in the developing lateral funiculus of the cervical spinal cord in fetal rhesus monkeys. The various macroglial cell types, their precursor cells, and microglia are discussed in detail. An astrocytic lineage is proposed in which glioblasts present in the lateral funiculus give rise to astroblasts that then develop into mature astrocytes. Oligoblasts apparently migrate into the lateral funiculus as such and develop into active oligocytes. The active oligocytes become most predominant during the initial stages of myelinogenesis and are in direct continuity with developing myelin. The active oligocytes develop into mature oligocytes after myelination is completed. Microglia cells are present throughout development as three forms; resting microglia, globose microglia, and active microglia. The globose and active microglia predominates at specific times early in development when degeneration of apparent neuronal processes is taking place. The microglia cells are characterized by dense nuclear chromatin clumps, lipid inclusion bodies, dense vesicles, and, often, intracellular debris.Supported in part by a Parson Trust Endowment Research Grant at the University of South Dakota School of Medicine. The author gratefully acknowledges the help of Dr. Ronald DiGiacomo who was responsible for the surgery involved in the fetal deliveries.     

Grading movement strength by changes in firing intensity versus recruitment of spinal interneurons

Animals can produce movements of widely varying speed and strength by changing the recruitment of motoneurons according to the well-known size principle. Much less is known about patterns of recruitment in the spinal interneurons that control motoneurons because of the difficulties of monitoring activity simultaneously in multiple interneurons of an identified class. Here we use electrophysiology in combination with in vivo calcium imaging of groups of identified excitatory spinal interneurons in larval zebrafish to explore how they are recruited during different forms of the escape response that fish use to avoid predators. Our evidence indicates that escape movements are graded largely by differences in the level of activity within an active pool of interneurons rather than by the recruitment of an inactive subset.     

Inhibition of crossed caudal interneurons by lateral interneurons in lamprey spinal cord during fictive locomotion

Templates of the membrane potential profiles from lateral (LI) interneurons and motoneurons during glutamate- and N-methyl-D-aspartate (NMDA)-induced fictive locomotion showed pronounced plateau phases. In contrast, crossed caudal (CC) interneurons had a less obvious and steeper plateau region that was followed by a clear notch coinciding with the end of the lateral interneuron plateau phase. These results indicate a significant inhibitory input from LI to CC interneurons.     

Nitric oxide synthase and interferon-gamma receptor immunoreactivities in relation to ascending spinal pathways to thalamus,hypothalamus, and the periaqueductal grey in the rat

The retrograde tracer fluoro-gold was injected into the periaqueductal grey, thalamus or hypothalamus, and spinal cord sections were processed for neuronal nitric oxide synthase (nNOS) immunohistochemistry to investigate the relationships of nNOS immunoreactive, and spinomesencephalic, spinothalamic and spinohypothalamic projection neurones. In addition, in the lateral spinal nucleus the relationship between spinomesencephalic, -thalamic and -hypothalamic projection neurones, and nNOS and interferon-gamma receptor immunoreactive structures was investigated at the lumbar level. No single retrogradely labelled spinomesencephalic, -thalamic or -hypothalamic neurone showed nNOS immunoreactivity. In the lateral spinal nucleus, however, many fluoro-gold-labelled neurones were closely apposed by both nNOS and interferon-gamma receptor immunoreactive structures, especially prominent in the hypothalamic injection cases. This study gave no evidence for nNOS immunoreactivity in spinal neurones projecting to the periaqueductal grey, thalamus or hypothalamus, but suggests that in the lateral spinal nucleus such neurones are contacted by both nNOS- and interferon-gamma receptor-containing axon terminals.     

A model of plant-to-plant movement of aphids III. Studies of actual movement and apparent movement by simulation technique

The plant-to-plant movement of aphids was investigated by the simulation technique in this report. Trials satisfying the following conditions are repeated and the results are compared withShiyomi 's model (1967).

1. An arbitrary individual moves at any moment.
2. The individual moves straightly forward an arbitrary direction and climbs up the plant that he first encounters with.
3. There is no concentrative birth and death.

Some of the results are as follows:

1. For an ideal state of movement, an equation describing the relationship between the frequency of actual movement and the degree of changes in the spatial distribution by movement was obtained.
2. The actual movements, whose frequency we cannot count, changes the spatial distribution of insects, and this change can be evaluated by the changes of values of the parameters contained inShiyomi 's model. Using the statement (i), we can also estimate the frequency of movements of aphids in the ideal (extreme) state.

     

Reactions of the rat musculoskeletal system to compressive spinal cord injury (SCI) and whole body vibration (WBV) therapy

Traumatic spinal cord injury (SCI) causes a loss of locomotor function with associated compromise of the musculo-skeletal system. Whole body vibration (WBV) is a potential therapy following SCI, but little is known about its effects on the musculo-skeletal system. Here, we examined locomotor recovery and the musculo-skeletal system after thoracic (T7-9) compression SCI in adult rats. Daily WBV was started at 1, 7, 14 and 28 days after injury (WBV1-WBV28 respectively) and continued over a 12-week post-injury period. Intact rats, rats with SCI but no WBV (sham-treated) and a group that received passive flexion and extension (PFE) of their hind limbs served as controls. Compared to sham-treated rats, neither WBV nor PFE improved motor function. Only WBV14 and PFE improved body support. In line with earlier studies we failed to detect signs of soleus muscle atrophy (weight, cross sectional diameter, total amount of fibers, mean fiber diameter) or bone loss in the femur (length, weight, bone mineral density). One possible explanation is that, despite of injury extent, the preservation of some axons in the white matter, in combination with quadripedal locomotion, may provide sufficient trophic and neuronal support for the musculoskeletal system.     

Differences between the tactile sensitivity on the anterior torso of normal individuals and those having suffered complete transection of the spinal cord

Using the method of limits and a magnitude estimation procedure, the sense of touch was examined at multiple sites on the anterior torso of normal subjects. Their performance was compared with the performance of individuals having experienced a functionally complete spinal cord transection more than 6 months prior to the tests. Near the insentient regions of the spinal cord-injured patients there was a zone wherein the threshold for light touch was elevated and variable. Within this same transition zone, estimates of the magnitude of a brushing stimulus increased as a linear function of distance from the border for approximately 12 cm away from insentient skin. Throughout the rest of the thorax, spinal cord-injured patients displayed touch thresholds 67% higher than normals and, at the same test sites, spinal cord-injured patients offered estimates of the intensity of the brushing stimulus that averaged 62% higher than normal subjects. The greater intensity of the sensations experienced by spinal cord-injured patients with even very weak stimuli and the smaller range within which they were able to scale stimulus intensity, produced a situation wherein the patients made frequent errors of judgement even on skin regions far from the body parts affected by the lesion. These observations support the hypothesis that spinal cord lesions interrupt tonic modulatory mechanisms having global influences on the sense of touch. This loss produces an elevation of the touch threshold and a reduction of the normal dynamic range of tactile sensory perception for all skin surfaces on the anterior torso.     

Time course changes to structural,mechanical and material properties of bone in rats after complete spinal cord injury

Objective:Characterise the spatiotemporal trabecular and cortical bone responses to complete spinal cord injury (SCI) in young rats.Methods:8-week-old male Wistar rats received T9-transection SCI and were euthanised 2-, 6-, 10- or 16-weeks post-surgery. Outcome measures were assessed using micro-computed tomography, mechanical testing, serum markers and Fourier-transform infrared spectroscopy.Results:The trabecular and cortical bone responses to SCI are site-specific. Metaphyseal trabecular BV/TV was 59% lower, characterised by fewer and thinner trabeculae at 2-weeks post-SCI, while epiphyseal BV/TV was 23% lower with maintained connectivity. At later-time points, metaphyseal BV/TV remained unchanged, while epiphyseal BV/TV increased. The total area of metaphyseal and mid-diaphyseal cortical bone were lower from 2-weeks and between 6- and 10-weeks post-SCI, respectively. This suggested that SCI-induced bone changes observed in the rat model were not solely attributable to bone loss, but also to suppressed bone growth. No tissue mineral density differences were observed at any time-point, suggesting that decreased whole-bone mechanical properties were primarily the result of changes to the spatial distribution of bone.Conclusion:Young SCI rat trabecular bone changes resemble those observed clinically in adult and paediatric SCI, while cortical bone changes resemble paediatric SCI only.     

Identification of key pathways and RNAs associated with skeletal muscle atrophy after spinal cord injury

Objective:This study was performed to investigate the potential key molecules involved in the progression of skeletal muscle atrophy after SCI.Methods:Based on {"type":"entrez-geo","attrs":{"text":"GSE21497","term_id":"21497"}}GSE21497 dataset, the DEmRNAs and DElncRNAs were screened after differentially expressed analysis. Then the enrichment analyses were performed on DEmRNAs. Then the PPI network and ceRNA network were constructed. Finally, the DGIdb was utilized to predict drug-gene interactions.Results:A total of 412 DEmRNAs and 21 DElncRNAs were obtained. The DEmRNAs were significantly enriched in MAPK signaling pathway and FoxO signaling pathway. In addition, UBE2D1, JUN, and FBXO32 had higher node degrees in PPI network, and the top 20 genes with high degree were significantly enriched in FoxO signaling pathway and Endometrial cancer. Moreover, FOXO3 was regulated by hsa-miR-1207-5p and hsa-miR-1207-5p was regulated by lncRNA RP11-253E3.3 in ceRNA network. Finally, 37 drug-gene interactions were obtained based on the 26 genes in ceRNA network.Conclusion:UBE2D1, JUN, and FBXO32 are likely to be related to the progression of skeletal muscle atrophy after SCI, and activating of MAPK signaling pathway, Endometrial cancer and FoxO signaling pathway may induce skeletal muscle inflammation, apoptosis, autophagy and atrophy after SCI. Moreover, RP11-253E3.3-hsa-miR-1207-5p-FOXO3 axis may be a promising therapeutic target for skeletal muscle atrophy after SCI.     

Anticipatory postural adjustments during sitting reach movement in post-stroke subjects

The study assessed the effect of velocity of arm movement on anticipatory postural adjustments (APAs) generation in the contralateral and ipsilateral muscles of individuals with stroke in seating. Ten healthy and eight post-stroke subjects were studied in sitting. The task consisted in reaching an object placed at scapular plane and mid-sternum height at self-selected and fast velocities. Electromyography was recorded from anterior deltoid (AD), upper (UT) and lower trapezius (LT) and latissimus dorsi (LD). While kinematic analysis was used to assess peak velocity and trunk displacement. Differences were found between the timing of APAs on ipsi and contralateral LD and LT in both movement speeds and in ipsilateral UT during movement of the non-affected arm at a self-selected velocity. A delay on the contralateral LD to reach movement with the non-affected arm at fast velocity was also observed. The trunk displacement was greater in post-stroke subjects. Individuals with stroke demonstrated a delay of APAs in the muscles on both sides of the body compared to healthy subjects. The delay was observed during performance of the reaching task with the fast and self-selected velocity.