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Rotator cuff (RC) disease is an extremely common condition associated with shoulder pain, reduced functional capacities, and impaired quality of life. It primarily involves alterations in tendon health and mechanical properties that can ultimately lead to tendon failure. RC tendon tears induce progressive muscle changes that have a negative impact on surgical reparability of the RC tendons and clinical outcomes. At the same time, a significant base of clinical data suggests a relatively weak relationship between RC integrity and clinical presentation, emphasizing the multifactorial aspects of RC disease. This review aims to summarize the potential contribution of peripheral, spinal, and supraspinal neural factors that may (1) exacerbate structural and functional muscle changes induced by tendon tear, (2) compromise the reversal of these changes during surgery and rehabilitation, (3) contribute to pain generation and persistence of pain, (4) impair shoulder function through reduced proprioception, kinematics, and muscle recruitment, and (5) help explain interindividual differences and response to treatment. Given the current clinical and scientific interest in peripheral nerve injury in the context of RC disease and surgery, we carefully reviewed this body of literature with a particular emphasis on suprascapular neuropathy that has generated a large number of studies in the past decade. Within this process, we highlight the gaps in current knowledge and suggest research avenues for scientists and clinicians.

Duchenne muscular dystrophy (DMD) is a devastating neuromuscular disease in which weakness, increased susceptibility to muscle injury, and inadequate repair underlie the pathology. While most attention has focused within the muscle fiber, we recently demonstrated significant alterations in the neuromuscular junction (NMJ) morphology and resulting neuromuscular transmission failure (NTF) 24 h after injury in mdx mice (murine model for DMD). Here we determine the contribution of NMJ morphology and NTF to the recovery of muscle contractile function post-injury. NMJ morphology and NTF rates were assessed day 0 (immediately after injury) and days 1, 7, 14 and 21 after quadriceps injury. Eccentric injury of the quadriceps resulted in a significant loss of maximal torque in both WT (39 ± 6 %) and mdx (76 ± 8 %) with a full recovery in WT by day 7 and in mdx by day 21. Post-injury alterations in NMJ morphology and NTF were found only in mdx, were limited to days 0 and 1, and were independent of changes in MuSK or AChR expression. Such early changes at the NMJ after injury are consistent with mechanical disruption rather than newly forming NMJs. Furthermore, we show that the dense microtubule network that underlies the NMJ is significantly reduced and disorganized in mdx compared to WT. These structural changes at the NMJ may play a role in the increased NMJ disruption and the exaggerated loss of nerve-evoked muscle force seen after injury to dystrophic muscles.

Duchenne muscular dystrophy (DMD) is a devastating neuromuscular disease in which weakness, increased susceptibility to muscle injury, and inadequate repair appear to underlie the pathology. While most attention has focused within the muscle fiber, we recently demonstrated in mdx mice (murine model for DMD) significant morphologic alterations at the motor endplate of the neuromuscular junction (NMJ) and corresponding NMJ transmission failure after injury. Here we extend these initial observations at the motor endplate to gain insight into the pre- vs. postsynaptic morphology, as well as the subsynaptic nuclei in healthy (WT) vs. mdx mice. We quantified the discontinuity and branching of the terminal nerve in adult mice. We report mdx- and age-dependent changes for discontinuity and an increase in branching when compared to WT. To examine mdx- and age-dependent changes in the relative localization of pre- and postsynaptic structures, we calculated NMJ occupancy, defined as the ratio of the footprint occupied by presynaptic vesicles vs. that of the underlying motor endplate. The normally congruent coupling between presynaptic and postsynaptic morphology was altered in mdx mice, independent of age. Finally we found an almost two-fold increase in the number of nuclei and an increase in density (nuclei/area) underlying the NMJ. These outcomes suggest substantial remodeling of the NMJ during dystrophic progression. This remodeling reflects plasticity in both pre- and postsynaptic contributors to NMJ structure, and thus perhaps also NM transmission and muscle function.

Local synthesis of proteins within the Schwann cell periphery is extremely important for efficient process extension and myelination, when cells undergo dramatic changes in polarity and geometry. Still, it is unclear how ribosomal distributions are developed and maintained within Schwann cell projections to sustain local translation. In this multi-disciplinary study, we expressed a plasmid encoding a fluorescently labeled ribosomal subunit (L4-GFP) in cultured primary rat Schwann cells. This enabled the generation of high-resolution, quantitative data on ribosomal distributions and trafficking dynamics within Schwann cells during early stages of myelination, induced by ascorbic acid treatment. Ribosomes were distributed throughout Schwann cell projections, with ~2-3 bright clusters along each projection. Clusters emerged within 1 day of culture and were maintained throughout early stages of myelination. Three days after induction of myelination, net ribosomal movement remained anterograde (directed away from the Schwann cell body), but ribosomal velocity decreased to about half the levels of the untreated group. Statistical and modeling analysis provided additional insight into key factors underlying ribosomal trafficking. Multiple regression analysis indicated that net transport at early time points was dependent on anterograde velocity, but shifted to dependence on anterograde duration at later time points. A simple, data-driven rate kinetics model suggested that the observed decrease in net ribosomal movement was primarily dictated by an increased conversion of anterograde particles to stationary particles, rather than changes in other directional parameters. These results reveal the strength of a combined experimental and theoretical approach in examining protein localization and transport, and provide evidence of an early establishment of ribosomal populations within Schwann cell projections with a reduction in trafficking following initiation of myelination.

BackgroundNerve cuff electrodes are commonly and successfully used for stimulating peripheral nerves. On the other hand, they occasionally induce functional and morphological changes following chronic implantation, for reasons not always clear. We hypothesize that restriction of nerve mobility due to cuff implantation may alter nerve conduction.MethodsWe quantified acute changes in nerve-muscle electrophysiology, using electromyography, and nerve kinematics in anesthetized Sprague Dawley rat sciatic nerves during controlled hindlimb joint movement. We compared electrophysiological and biomechanical response in uncuffed nerves and those secured within a cuff electrode using analysis of variance (ANOVA) and regression analysis.ResultsTethering resulting from cuff implantation resulted in altered nerve strain and a complex biomechanical environment during joint movement. Coincident with biomechanical changes, electromyography revealed significantly increased variability in the response of conduction latency and amplitude in cuffed, but not free, nerves following joint movement.ConclusionOur findings emphasize the importance of the mechanical interface between peripheral nerves and their devices on neurophysiological performance. This work has implications for nerve device design, implantation, and prediction of long-term efficacy.

Peripheral nerve damage is one consequence of injury to the extremities of soldiers by improvised explosive devices (IEDs). The degree of functional recovery from peripheral nerve damage is often poor, particularly for severed nerves. The result can be impaired motor function, sensory loss, and chronic pain with inappropriate autonomic responses. Consequently, strategies for enhancing nervous function are of high military relevance. Towards the development of more effective nerve regeneration strategies, this proposal addresses the hypothesis that moderate tensile loading (stretch) of peripheral nerves can stabilize nerve degradation and also promote accelerated regeneration. Our project aims are to 1) To examine the impact of low levels of tensile loading on the Wallerian degeneration of proximal and distal stumps of severed peripheral nerves and 2) To examine the impact of moderate levels of tensile loading on promoting the outgrowth and functional connectivity of severed peripheral nerves. To meet these aims, in the final project period, based on results from initial in vivo implantations, we completed characterization of proximal and distal nerve stumps following 3-6 weeks of device implantation. No adverse effects were observed following 20% initial deformation, suggesting that, at minimum, tension provides a head start for nerve regeneration. Long-term survival surgeries will be required to formally test whether functional recovery is accelerated., The original document contains color images.

Translation of mRNA in axons and dendrites enables a rapid supply of proteins to specific sites of localization within the neuron. Distinct mRNA-containing cargoes, including granules and mitochondrial mRNA, are transported within neuronal projections. The distributions of these cargoes appear to change during neuronal development, but details on the dynamics of mRNA transport during these transitions remain to be elucidated. For this study, we have developed imaging and image processing methods to quantify several transport parameters that can define the dynamics of RNA transport and localization. Using these methods, we characterized the transport of mitochondrial and non-mitochondrial mRNA in differentiated axons and dendrites of cultured hippocampal neurons varying in developmental maturity. Our results suggest differences in the transport profiles of mitochondrial and non-mitochondrial mRNA, and differences in transport parameters at different time points, and between axons and dendrites. Furthermore, within the non-mitochondrial mRNA pool, we observed two distinct populations that differed in their fluorescence intensity and velocity. The net axonal velocity of the brighter pool was highest at day 7 (0.002±0.001 µm/s, mean ± SEM), raising the possibility of a presynaptic requirement for mRNA during early stages of synapse formation. In contrast, the net dendritic velocity of the brighter pool increased steadily as neurons matured, with a significant difference between day 12 (0.0013±0.0006 µm/s ) and day 4 (-0.003±0.001 µm/s) suggesting a postsynaptic role for mRNAs in more mature neurons. The dim population showed similar trends, though velocities were two orders of magnitude higher than of the bright particles. This study provides a baseline for further studies on mRNA transport, and has important implications for the regulation of neuronal plasticity during neuronal development and in response to neuronal injury.

Peripheral nerve damage is one consequence of injury to the extremities of soldiers by improvised explosive devices (IEDs). The degree of functional recovery from peripheral nerve damage is often poor, particularly for severed nerves. The result can be impaired motor function, sensory loss, and chronic pain with inappropriate autonomic responses. Consequently, strategies for enhancing nervous function are of high military relevance. Towards the development of more effective nerve regeneration strategies, this proposal addresses the hypothesis that moderate tensile loading (stretch) of peripheral nerves can stabilize nerve degradation and also promote accelerated regeneration. Our project aims are to 1) To examine the impact of low levels of tensile loading on the Wallerian degeneration of proximal and distal stumps of severed peripheral nerves and 2) To examine the impact of moderate levels of tensile loading on promoting the outgrowth and functional connectivity of severed peripheral nerves. To meet these aims, in the second project period, based on results from initial in vivo implantations, we modified our two nerve lengthening devices, one a fixed length and one extensible, and are currently performing long-term implantations to test the effectiveness of these devices for nerve regeneration.

Objective: To develop pharmacognostical and quality control parameters for drug Sarcostemma brevistigma Wight and Arn. (Family: Asclepiadaceae) commonly known as Somlata, is rasayana drug. Materials and Methods: Stems of S. brevistigma were collected from Jamnagar, Dwarka and Bhuj in the month of November 2008 and studied for macroscopical and microscopical characters. Quantitative microscopy and physico-chemical parameters were also performed. A pregnane derivative mono-O-acetyl bregenin was isolated from stem extract and characterized by U.V., IR, NMR, Mass spectroscopy. HPTLC method was developed to quantify mono-O-acetyl bregenin and generate fingerprint profile for the drug. HPTLC was performed using precoated TLC plate (silica gel 60 F254) as a stationary phase and Chloroform : Methanol (9.4 : 0.6) as a mobile phase. The plate was scanned at 366nm. Results: Macroscopically and microscopically all the samples of stems were found to be similar but differed in quantitative parameters. Stems were green, cylindrical in shape having longitudinal ridges and nodes. T.S. of stems showed papillose epidermis, rosettes of calcium oxalate, non lignified fibres and latex cavities in cortex, striated cells of inner cortex and perimedullary phloem. Stone cells and abundant rosettes of calcium oxalate were found in section passing through the node. Powder showed stone cells, rosettes, fragments of pitted xylem vessels and non lignified fibres. Mono-O-acetyl bregenin was isolated by column chromatography. HPTLC chromatogram was developed and blue fluorescent spot was visualised at Rf 0.5 under UV at 366nm. Mono-O-acetyl bregenin content was found to be 0.0339% w/w, 0.0399% w/w, 0.0227% w/w in samples collected from Jamnagar, Dwarka and Bhuj respectively.

Mutations in superoxide dismutase (SOD1) are causative for inherited amyotrophic lateral sclerosis. A proportion of SOD1 mutant protein is misfolded onto the cytoplasmic face of mitochondria in one or more spinal cord cell types. By construction of mice in which mitochondrially targeted enhanced green fluorescent protein is selectively expressed in motor neurons, we demonstrate that axonal mitochondria of motor neurons are primary in vivo targets for misfolded SOD1. Mutant SOD1 alters axonal mitochondrial morphology and distribution, with dismutase active SOD1 causing mitochondrial clustering at the proximal side of Schmidt-Lanterman incisures within motor axons and dismutase inactive SOD1 producing aberrantly elongated axonal mitochondria beginning pre-symptomatically and increasing in severity as disease progresses. Somal mitochondria are altered by mutant SOD1, with loss of the characteristic cylindrical, networked morphology and its replacement by a less elongated, more spherical shape. These data indicate that mutant SOD1 binding to mitochondria disrupts normal mitochondrial distribution and size homeostasis as early pathogenic features of SOD1 mutant-mediated ALS.