Tibialis Cranialis Muscle Research Articles

Stem cells in end-to-side neurorrhaphy. Experimental study in rats.

Purpose:To evaluate the influence of mesenchymal stem cells from adipose tissue in the end-to-side neurorrhaphy, focusing in the nerve regeneration and the muscle reinnervation in acute trauma.Methods:140 animals were randomly divided in seven groups: control, denervated, end-to-side neurorrhaphy between distal stump of common peroneal nerve and tibial nerve (ESN), ESN wrapped in fascia, ESN wrapped in fascia and platelet gel, ESN wrapped in platelet gel, ESN wrapped in fascia and platelet gel within stem cells (without culture) removed from the adipose tissue. Mass measurements of the animal and of cranial tibial muscles, electromyography, walking track analysis tests and histological examinations of the nerves and muscles after 180 days was performed.Results:In the groups where the ESN was performed, the results were always better when compared to the denervated group, showing reinnervation in all ESN groups. The most sensitive methods were walking track and histological analysis. Only the group with stem cells showed values similar to the control group, as well as the functional indices of peroneal nerve and the number of nerve fibers in the peroneal nerve.Conclusions:Stem cells were effective in ESN according with the functional index of the peroneal nerve, evaluated by walking track analysis and the number of nerve fibers in the peroneal nerve.

Laminin-111 protein therapy enhances muscle regeneration and repair in the GRMD dog model of Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a devastating X-linked disease affecting ~1 in 5000 males. DMD patients exhibit progressive muscle degeneration and weakness, leading to loss of ambulation and premature death from cardiopulmonary failure. We previously reported that mouse Laminin-111 (msLam-111) protein could reduce muscle pathology and improve muscle function in the mdx mouse model for DMD. In this study, we examined the ability of msLam-111 to prevent muscle disease progression in the golden retriever muscular dystrophy (GRMD) dog model of DMD. The msLam-111 protein was injected into the cranial tibial muscle compartment of GRMD dogs and muscle strength and pathology were assessed. The results showed that msLam-111 treatment increased muscle fiber regeneration and repair with improved muscle strength and reduced muscle fibrosis in the GRMD model. Together, these findings support the idea that Laminin-111 could serve as a novel protein therapy for the treatment of DMD.

Clinical outcomes after common calcanean tendon rupture repair in dogs with a loop-suture tenorrhaphy technique and autogenous leukoreduced platelet-rich plasma.

To report outcomes of dogs with common calcanean tendon (CCT) ruptures treated with a platelet-rich plasma (PRP) enhanced nonabsorbable loop-suture technique. Retrospective case series. Client-owned dogs (n = 12). Medical records (2015-2017) of dogs with CCT ruptures repaired with a loop-suture tenorrhaphy and autogenous leukoreduced PRP were reviewed for signalment, history, type of injury, treatment, and clinical follow-up. Outcomes were assessed by functional anatomic measurements and Canine Orthopedic Index (COI) scores transformed to percentages, with 100% representing no problems. Twelve tendons were treated. Two dogs had major complications that were successfully revised. Follow-up was available in 11 of 12 dogs, with a median time of 12 months (range, 4-36), including COI for 11 dogs and anatomic measurements for 6 dogs. Anatomic measurements did not differ between treated and normal contralateral limbs (midthigh muscle mass P > .99, cranial tibial muscle mass P = .37, CCT diameter P = .08, tibiotarsal joint angle P > .99). Owners scored function (COI) as 96.4% (range, 93.3%-97.8%) and quality of life as 94.6% (range, 92%-98.2%). Loop-suture tenorrhaphy with application of autogenous leukoreduced PRP at the repair site resulted in restoration of functional anatomic measurements, high COI, and client satisfaction. Loop-suture tenorrhaphy with local application of autogenous leukoreduced PRP appears to offer an acceptable option to treat CCT injuries in dogs.

Sciatic Nerve Injection Palsy in a Dog: Electrodiagnostic Testing and Microsurgical Treatment

Background: Iatrogenic damage to the ischiatic nerve is considered uncommon and may cause dysfunction with variable clinical signs dependent on type and severity of injury. Due to important role of this nerve in locomotion and weightbearing limb, a poor prognosis for recovery may be observed in many cases. Electromyography analysis may suggest the neuroanatomic localization, diagnosis information, and severity of lesion to determine better therapeutic intervention. Therefore, the aim of this report is to describe the possible cause, diagnosis and treatment of a postinjection ischiatic nerve injury in a dog with complete recovery.Case: A 3-year-old neutered male dachshund dog was referred to the Veterinary Hospital due to inability to weight support in the right hind limb after diminazene diaceturate intramuscular injection. The gait evaluation showed dropped-hock and knuckling into the digits of the right hind limb and neurologic examination revealed moderate muscle atrophy below tofemorotibial joint of the right hind limb with sensory analgesia (superficial and deep) on the lateral, dorsal, and plantar surfaces, absent patellar reflex, and proprioceptive deficit. Electrophysiologic testing was done under general anesthesia in a 2-channel Nicolet Compass Meridian apparatus. Absence of compound muscle action potentials after right fibular and tibial nerve stimulations, and abnormal spontaneous activity in cranial tibial, gastrocnemius and deep digital extensor muscles were observed. A diagnosis of moderate/severe axonotmesis of sciatic nerve was achieved. Under microscope magnification, all adherent adjacent tissue and epineural sheat were removed. Due this, a small epineural window was created. On neurological examination performed 30 days after surgery, complete recovery of sensitivity of the right hind limb, and normal proprioception were observed. The muscle atrophy was also noted to have improved.Discussion: The ischiatic nerve mechanisms of injury include direct needle trauma, the drug or vehicle used for injection, or secondary constriction by scar, factors that may be associated to damage nerve observed in the present case. During a sciatic nerve injection, the combination of intrafascicular placement of a needle and high-pressure injection may cause severe fascicular damage and persistent neurologic deficits. In the present case, damage to the nerve probably was not caused bythe injection needle, but due to injection agent. Chemical irritation or toxic reaction to the agent may cause different degrees of nerve injury. The electrophysiologic testing is an important tool for determining alteration of function and integrity of the axonal motor unit. In the present report, the electrophysiologic testing showed denervation potentials in the musclesinnervated by the sciatic nerve (positive waves and fibrillation potentials), and the absence of compound muscle action potentials was indicative of severe axonal damage of the right ischiatic nerve. In human patients with postinjection ischiatic nerve injury, early surgical treatment with neurolysis or resection and anastomosis are the procedures recommended. In the present report, external neurolysis and epineural window were used showing excellent functional results. The epineural window was performed due to adherence of tissue and scar surrounding the nerve, permitting neural decompression.Keywords: axonotmesis, neurophysiology, neurolysis, dogs.

Temporal changes in macrophage phenotype after peripheral nerve injury

BackgroundMacrophages play a key role in peripheral nerve repair and demonstrate complex phenotypes that are highly dependent on microenvironmental cues.MethodsWe determined temporal changes in macrophage gene expression over time using RNA sequencing after fluorescence-activated cell sorting (FACS) macrophage populations from injured peripheral nerve. We identified key upstream regulators and dominant pathways using ingenuity pathway analysis and confirmed these changes with NanoString technology. We then investigate the effects of extreme polarizers of macrophage phenotype (IL4 and IFNγ) on nerve regeneration. We determined macrophage gene expression in vivo at the site of peripheral nerve injury with NanoString technology, and assessed recovery from sciatic nerve injury by cranial tibial muscle weights and retrograde labeling motor neurons in mice with deletion of IL4 or IFNγ receptors.ResultsWe demonstrate that IL4R and IFNγR deletions provide complementary responses to polarization, and alter expression of genes associated with angiogenesis and axonal extension, but do not influence recovery from peripheral nerve transection at 8 weeks after repair.ConclusionsOverall, this study provides a framework to evaluate the phenotype of macrophages over time, and provides a broader and more precise assessment of gene expression changes than has previously been commonly used. This data suggests ways in which polarization may be modulated to improve repair.

Multipulse transcranial electrical stimulation (TES): normative data for motor evoked potentials in healthy horses

BackgroundThere are indications that transcranial electrical stimulation (TES) assesses the motor function of the spinal cord in horses in a more sensitive and reproducible fashion than transcranial magnetic stimulation (TMS). However, no normative data of TES evoked motor potentials (MEP) is available.ResultsIn this prospective study normative data of TES induced MEP wave characteristics (motor latency times (MLT); amplitude and waveform) was obtained from the extensor carpi radialis (ECR) and tibial cranialis (TC) muscles in a group of healthy horses to create a reference frame for functional diagnostic purposes. For the 12 horses involved in the study 95% confidence intervals for MLTs were 16.1–22.6 ms and 31.9–41.1 ms for ECR and TC muscles respectively. Intra-individual coefficients of variation (CV) and mean of MLTs were: ECR: 2.2–8,2% and 4.5% and TC: 1.4–6.3% and 3.5% respectively. Inter-individual CVs for MLTs were higher, though below 10% on all occasions.The mean ± sd of MEP amplitudes was respectively 3.61 ± 2.55 mV (ECR muscle left) and 4.53 ± 3.1 mV (right) and 2.66 ± 2.22 mV (TC muscle left) and 2.55 ± 1.85 mV (right). MLTs showed no significant left versus right differences.All MLTs showed significant (p < 0.05) voltage dependent decreases with slope coefficients of linear regression for ECR: − 0.049; − 0.061 ms/V and TC: − 0.082; − 0.089 ms/V (left; right). There was a positive correlation found between height at withers and MLTs in all 4 muscle groups. Finally, reliable assessment of MEP characteristics was for all muscle groups restricted to a transcranial time window of approximately 15–19 ms.ConclusionsTES is a novel and sensitive technique to assess spinal motor function in horses. It is easy applicable and highly reproducible. This study provides normative data in healthy horses on TES induced MEPs in the extensor carpi radialis and tibialis cranialis muscles bilaterally. No significant differences between MLTs of the left and right side could be demonstrated. A significant effect of stimulation voltage on MLTs was found. No significant effect of height at the withers could be found based upon the results of the current study. A study in which both TMS and TES are applied on the same group of horses is needed.

Myositis, Ganglioneuritis, and Myocarditis with Distinct Perifascicular Muscle Atrophy in a 2-Year-Old Male Boxer

A 2-year-old male, intact Boxer was referred for chronic diarrhea, hyporexia, labored breathing, weakness and elevated creatine kinase, and alanine aminotransferase activities. Initial examination and diagnostics revealed a peripheral nervous system neurolocalization, atrial premature complexes, and generalized megaesophagus. Progressive worsening of the dog’s condition was noted after 36 h; the dog developed aspiration pneumonia, was febrile and oxygen dependent. The owners elected humane euthanasia. Immediately postmortem biopsies of the left cranial tibial and triceps muscles and the left peroneal nerve were obtained. Postmortem histology revealed concurrent myositis, myocarditis, endocarditis, and ganglioneuritis. Mixed mononuclear cell infiltrations and a distinct perifascicular pattern of muscle fiber atrophy was present in both muscles. This is a novel case of diffuse inflammatory myopathy with a distinct perifascicular pattern of atrophy in addition to endocarditis, myocarditis, and epicarditis.

Efficient Non-Invasive Plasmid-DNA Administration into Tibialis Cranialis Muscle of "Little" Mice.

An alternative treatment for growth hormone deficiency based on hGH-DNA administration, followed by electro gene transfer, was investigated by injecting the plasmid into surgically exposed or non-exposed quadriceps or tibialis muscle of immunodeficient "little" mice. An optimization of electrotransfer conditions via a new combination of high/low voltage pulses is presented. After 3 days, serum hGH was determined and in a 28-day assay, the relative growth parameters were compared. Both groups exhibited similar results: 5.0 ± 2.2 (SD) and 3.5 ± 0.9 ng hGH/ml (P>0.05; n=7) for the exposed quadriceps and non-exposed tibialis treatments, respectively. The final body weight increases were 16.1% for the quadriceps and 18.9% for the tibialis group. The tail and nose-to-tail length increases were 4.5% and 7.1% for the quadriceps and 4.8 and 4.6% for the tibialis group. The right and left femur length increases, obtained from radiographic measurements, were 16.9% and 12.7% for the quadriceps and 19.4% and 12.3% for the tibialis, respectively. A non-significant difference between exposed quadriceps and non-exposed tibialis treatments (P=0.48) was confirmed via a completely integrated statistical analysis. Circulating mIGF-1 levels were 126 ± 47, 106 ± 93 (P>0.05) and 38 ± 15 ng/ml for the quadriceps, tibialis and saline treatments, respectively. These results show that hGH-DNA administration into non-exposed tibialis muscle followed by the new HV/LV electrotransfer protocol was an equally efficient, less traumatic treatment, much more suitable for pre-clinical testing than administration into exposed quadriceps.

End-to-side versus end-to-end neurorrhaphy at the peroneal nerve in rats

To evaluate three different kinds of neurorrhaphy of the peroneal nerve. Eigthy rats were divided into 5 groups. Control: nerve had no intervention. End-to-end (EE): nerve was cut and elongated with a nerve graft with two end-to-end neurorrhaphies. End-to-side (ES): nerve was cut and sutured to the graft with at the lateral side of the nerve. Side-to-end (SE): the nerve was cut and sutured to the graft with end-to-end neurorrhaphy. Denervated: nerve was cut and both endings were buried into the muscle. The evaluation was done by walking track analysis, electrophysiology, body mass, cranial tibial muscle mass, nerve and muscle fibers morphometry. The EE, ES and SE have the same potential of reinnervation. There is no functional or histological difference between these different types of neurorrhaphy.

Obesity-induced discrepancy between contractile and metabolic phenotypes in slow- and fast-twitch skeletal muscles of female obese Zucker rats.

A clear picture of skeletal muscle adaptations to obesity and related comorbidities remains elusive. This study describes fiber-type characteristics (size, proportions, and oxidative enzyme activity) in two typical hindlimb muscles with opposite structure and function in an animal model of genetic obesity. Lesser fiber diameter, fiber-type composition, and histochemical succinic dehydrogenase activity (an oxidative marker) of muscle fiber types were assessed in slow (soleus)- and fast (tibialis cranialis)-twitch muscles of obese Zucker rats and compared with age (16 wk)- and sex (females)-matched lean Zucker rats (n = 16/group). Muscle mass and lesser fiber diameter were lower in both muscle types of obese compared with lean animals even though body weights were increased in the obese cohort. A faster fiber-type phenotype also occurred in slow- and fast-twitch muscles of obese rats compared with lean rats. These adaptations were accompanied by a significant increment in histochemical succinic dehydrogenase activity of slow-twitch fibers in the soleus muscle and fast-twitch fiber types in the tibialis cranialis muscle. Obesity significantly increased plasma levels of proinflammatory cytokines but did not significantly affect protein levels of peroxisome proliferator-activated receptors PPARγ or PGC1α in either muscle. These data demonstrate that, in female Zucker rats, obesity induces a reduction of muscle mass in which skeletal muscles show a diminished fiber size and a faster and more oxidative phenotype. It was noteworthy that this discrepancy in muscle's contractile and metabolic features was of comparable nature and extent in muscles with different fiber-type composition and antagonist functions.NEW & NOTEWORTHY This study demonstrates a discrepancy between morphological (reduced muscle mass), contractile (shift toward a faster phenotype), and metabolic (increased mitochondrial oxidative enzyme activity) characteristics in skeletal muscles of female Zucker fatty rats. It is noteworthy that this inconsistency was comparable (in nature and extent) in muscles with different structure and function.

Morphological and molecular identification of Sarcocystis arctica sarcocysts in three red foxes (Vulpes vulpes) from the Czech Republic

Muscular sarcocystosis by Sarcocystis arctica was found for the first time in the Czech Republic, in different muscles of red fox (Vulpes vulpes). Cysts were slim, elongated, thread-like, whitish, 1–7mm long, and 206–270μm wide; bradyzoites were 7.9×2.7μm in unstained wet mounts and 9.2×2.9μm in cyst Giemsa-stained smears. The cyst wall was thin, with short villi-like protrusions, and no host response was observed in the histological sections. Examination of the distribution and intensity of sarcocysts in 17 different muscle groups revealed that the highest intensity was in the cranial tibial muscle (>15 cysts in compressoria), followed by the diaphragm, forearm, and other groups (with intensities of 3–15 cysts in compressoria). Sarcocysts were detected in 3 out of 86 foxes. Genetic characterization at 18S rRNA, 28S rRNA, ITS1 and cox1, consistently showed that the species was identical with S. arctica. Interestingly, this protozoan was also detected as a co-infection in 3 foxes with the nematode Trichinella spp. for the first time.

Mangiferin protects against adverse skeletal muscle changes and enhances muscle oxidative capacity in obese rats.

Obesity-related skeletal muscle changes include muscle atrophy, slow-to-fast fiber-type transformation, and impaired mitochondrial oxidative capacity. These changes relate with increased risk of insulin resistance. Mangiferin, the major component of the plant Mangifera indica, is a well-known anti-inflammatory, anti-diabetic, and antihyperlipidemic agent. This study tested the hypothesis that mangiferin treatment counteracts obesity-induced fiber atrophy and slow-to-fast fiber transition, and favors an oxidative phenotype in skeletal muscle of obese rats. Obese Zucker rats were fed gelatin pellets with (15 mg/kg BW/day) or without (placebo group) mangiferin for 8 weeks. Lean Zucker rats received the same gelatin pellets without mangiferin and served as non-obese and non-diabetic controls. Lesser diameter, fiber composition, and histochemical succinic dehydrogenase activity (an oxidative marker) of myosin-based fiber-types were assessed in soleus and tibialis cranialis muscles. A multivariate discriminant analysis encompassing all fiber-type features indicated that obese rats treated with mangiferin displayed skeletal muscle phenotypes significantly different compared with both lean and obese control rats. Mangiferin significantly decreased inflammatory cytokines, preserved skeletal muscle mass, fiber cross-sectional size, and fiber-type composition, and enhanced muscle fiber oxidative capacity. These data demonstrate that mangiferin attenuated adverse skeletal muscle changes in obese rats.

Transcranial magnetic stimulation with acepromazine or dexmedetomidine in combination with levomethadone/fenpipramide in healthy Beagle dogs

The aim of this study was to evaluate the influence of two sedation protocols on transcranial magnetic motor evoked potentials (TMMEPs) after transcranial magnetic stimulation in medium sized dogs. Onset latencies and peak-to-peak amplitudes, elicited in the extensor carpi radialis and cranial tibial muscles, were analysed in 10 healthy Beagles that received either acepromazine or dexmedetomidine in combination with levomethadone/fenpipramide, in a crossover design. Similar TMMEP recordings could be made using both sedation protocols at 80–90% stimulation intensity; however, there were significantly shorter onset latencies with the acepromazine-levomethadone/fenpipramide protocol at 100% stimulation intensity. Reference values were established and it was concluded that both drug combinations are feasible for measuring TMMEPs in medium sized dogs.

Impairment of toll-like receptors 2 and 4 leads to compensatory mechanisms after sciatic nerve axotomy.

BackgroundPeripheral nerve injury results in retrograde cell body-related changes in the spinal motoneurons that will contribute to the regenerative response of their axons. Successful functional recovery also depends on molecular events mediated by innate immune response during Wallerian degeneration in the nerve microenvironment. A previous study in our lab demonstrated that TLR 2 and 4 develop opposite effects on synaptic stability in the spinal cord after peripheral nerve injury. Therefore, we suggested that the better preservation of spinal cord microenvironment would positively influence distal axonal regrowth. In this context, the present work aimed to investigate the influence of TLR2 and TLR4 on regeneration and functional recovery after peripheral nerve injury.MethodsEighty-eight mice were anesthetized and subjected to unilateral sciatic nerve crush (C3H/HeJ, n = 22, C3H/HePas, n = 22; C57Bl6/J, n = 22 and TLR2−/−, n = 22). After the appropriate survival times (3, 7, 14 days, and 5 weeks), all mice were killed and the sciatic nerves and tibialis cranialis muscles were processed for immunohistochemistry and transmission electron microscopy (TEM). Gait analysis, after sciatic nerve crushing, was performed in another set of mice (minimum of n = 8 per group), by using the walking track test (CatWalk system).ResultsTLR4 mutant mice presented greater functional recovery as well as an enhanced p75NTR and neurofilament protein expression as compared to the wild-type strain. Moreover, the better functional recovery in mutant mice was correlated to a greater number of nerve terminal sprouts. Knockout mice for TLR2 exhibited 30 % greater number of degenerated axons in the distal stump of the sciatic nerve and a decreased p75NTR and neurofilament protein expression compared to the wild type. However, the absence of TLR2 receptor did not influence the overall functional recovery. End-point equivalent functional recovery in transgenic mice may be a result of enhanced axonal diameter found at 2 weeks after lesion.ConclusionsAltogether, the present results indicate that the lack of TLR2 or the absence of functional TLR4 does affect the nerve regeneration process; however, such changes are minimized through different compensatory mechanisms, resulting in similar motor function recovery, as compared to wild-type mice. These findings contribute to the concept that innate immune-related molecules influence peripheral nerve regeneration by concurrently participating in processes taking place both at the CNS and PNS.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0579-6) contains supplementary material, which is available to authorized users.

Noninvasive optical diagnostics of enhanced green fluorescent protein expression in skeletal muscle for comparison of electroporation and sonoporation efficiencies.

We highlight the options available for noninvasive optical diagnostics of reporter gene expression in mouse tibialis cranialis muscle. An in vivo multispectral imaging technique combined with fluorescence spectroscopy point measurements has been used for the transcutaneous detection of enhanced green fluorescent protein (EGFP) expression, providing information on location and duration of EGFP expression and allowing quantification of EGFP expression levels. For EGFP coding plasmid (pEGFP-Nuc Vector, 10 μg/50 ml 10 μg/50 ml ) transfection, we used electroporation or ultrasound enhanced microbubble cavitation [sonoporation (SP)]. The transcutaneous EGFP fluorescence in live mice was monitored over a period of one year using the described parameters: area of EGFP positive fibers, integral intensity, and mean intensity of EGFP fluorescence. The most efficient transfection of EGFP coding plasmid was achieved, when one high voltage and four low voltage electric pulses were applied. This protocol resulted in the highest short-term and long-term EGFP expression. Other electric pulse protocols as well as SP resulted in lower fluorescence intensities of EGFP in the transfected area. We conclude that noninvasive multispectral imaging technique combined with fluorescence spectroscopy point measurements is a suitable method to estimate the dynamics and efficiency of reporter gene transfection in vivo.

Widespread somatosensory sensitivity in naturally occurring canine model of osteoarthritis.

Osteoarthritis (OA)-associated pain is a leading cause of disability. Central sensitization (CS), as a result of OA, is recognized as an important facet of human patients' chronic pain and has been measured in people using quantitative sensory testing (QST) testing. The spontaneous canine OA model has been suggested as a good translational model, but CS has not been explored in this model. In this study, QST was performed on dogs with and without spontaneous hip or stifle OA to determine whether OA is associated with CS in this model. Mechanical (von Frey and blunt pressure) and thermal (hot and cold) sensory thresholds obtained in dogs with chronic OA-associated pain (n = 31) were compared with those of normal dogs (n = 23). Dogs were phenotyped and joint-pain scored, and testing was performed at the OA-affected joint, cranial tibial muscle, and dorsal metatarsal region. QST summary data were evaluated using mixed-effect models to understand the influence of OA status and covariates, and dogs with OA and control dogs were compared. The presence of OA was strongly associated with hyperalgesia across all QST modalities at the index joint, cranial tibial muscle, and metatarsal site. Mechanical QST scores were significantly moderately negatively correlated with total joint-pain scores. The spontaneous canine OA model is associated with somatosensory sensitivity, likely indicative of CS. These data further validate the canine spontaneous OA model as an appropriate model of the human OA pain condition.

High-phosphorus diet maximizes and low-dose calcitriol attenuates skeletal muscle changes in long-term uremic rats.

Although disorders of mineral metabolism and skeletal muscle are common in chronic kidney disease (CKD), their potential relationship remains unexplored. Elevations in plasma phosphate, parathyroid hormone, and fibroblastic growth factor 23 together with decreased calcitriol levels are common features of CKD. High-phosphate intake is a major contributor to progression of CKD. This study was primarily aimed to determine the influence of high-phosphate intake on muscle and to investigate whether calcitriol supplementation counteracts negative skeletal muscle changes associated with long-term uremia. Proportions and metabolic and morphological features of myosin-based muscle fiber types were assessed in the slow-twitch soleus and the fast-twitch tibialis cranialis muscles of uremic rats (5/6 nephrectomy, Nx) and compared with sham-operated (So) controls. Three groups of Nx rats received either a standard diet (0.6% phosphorus, Nx-Sd), or a high-phosphorus diet (0.9% phosphorus, Nx-Pho), or a high-phosphorus diet plus calcitriol (10 ng/kg 3 day/wk ip, Nx-Pho + Cal) for 12 wk. Two groups of So rats received either a standard diet or a high-phosphorus diet (So-Pho) over the same period. A multivariate analysis encompassing all fiber-type characteristics indicated that Nx-Pho + Cal rats displayed skeletal muscle phenotypes intermediate between Nx-Pho and So-Pho rats and that uremia-induced skeletal muscle changes were of greater magnitude in Nx-Pho than in Nx-Sd rats. In uremic rats, treatment with calcitriol preserved fiber-type composition, cross-sectional size, myonuclear domain size, oxidative capacity, and capillarity of muscle fibers. These data demonstrate that a high-phosphorus diet potentiates and low-dose calcitriol attenuates adverse skeletal muscle changes in long-term uremic rats.

In vivo simultaneous evaluations of sarcomere imaging and muscle fiber tension

Muscle fiber tension and sarcomere length play critical roles in regulating muscle functions and adaptations under pathological conditions. However, methods are lacking to quantify these two variables simultaneously in vivo. A novel force microscope was developed with the unique capabilities of estimating muscle fiber tension and acquiring sarcomere images simultaneously in vivo. The force microscope consisting of a custom microscopic imaging system and a force sensor was used to quantify in vivo sarcomere length, muscle fiber tension and stress of the tibialis cranialis muscle at plantar-flexed and dorsi-flexed positions from 11 rat hind limbs. Results showed that sarcomere images and fiber tension could be measured together in vivo with significantly higher muscle fiber tension and stress and longer sarcomere length at the plantar-flexed position when compared to their counterparts at the dorsi-flexed position. The fiber tension estimated using the force microscope had close agreement with the direct measurements of the fiber tension. The present force microscope with simultaneous characterizations of fiber tension and sarcomere imaging provides us a useful in vivo tool to investigate the roles of muscle tension in regulating sarcomere and muscle fiber functions under physiological and pathological conditions.

Partial correction of the dwarf phenotype by non-viral transfer of the growth hormone gene in mice: Treatment age is critical

Non-viral transfer of the growth hormone gene to different muscles of immunodeficient dwarf (lit/scid) mice is under study with the objective of improving phenotypic correction via this particular gene therapy approach. Plasmid DNA was administered into the exposed quadriceps or non-exposed tibialis cranialis muscle of lit/scid mice followed by electroporation, monitoring several growth parameters. In a 6-month bioassay, 50μg DNA were injected three times into the quadriceps muscle of 80-day old mice. A 50% weight increase, with a catch-up growth of 21%, together with a 16% increase for nose-to-tail and tail lengths (catch-up=19–21%) and a 24–28% increase for femur length (catch-up=53–60%), were obtained. mIGF1 serum levels were ~7-fold higher than the basal levels for untreated mice, but still ~2-fold lower than in non-dwarf scid mice. Since treatment age was found to be particularly important in a second bioassay utilizing 40-day old mice, these pubertal mice were compared in a third bioassay with adult (80-day old) mice, all treated twice with 50μg DNA injected into each tibialis cranialis muscle, via a less invasive approach. mIGF1 concentrations at the same level as co-aged scid mice were obtained 15days after administration in pubertal mice. Catch-up growth, based on femur length (77%), nose-to-tail (36%) and tail length (39%) increases was 40 to 95% higher than those obtained upon treating adult mice. These data pave the way for the development of more effective pre-clinical assays in pubertal dwarf mice for the treatment of GH deficiency via plasmid-DNA muscular administration.

The Potential Role of Motor Unit Number Estimation as an Additional Diagnostic and Prognostic Value in Canine Neurology.

Motor unit number estimation (MUNE) is an electrophysiological technique to assess the number of motor units innervating a single muscle or muscle group of interest. It may quantify axonal loss in any disease involving injury or degeneration of ventral horn cells or motor axons. Since MUNE has rarely been used in veterinary medicine, our study aimed to evaluate its potential role as an additional diagnostic and prognostic parameter in canine neurology. Therefore, we examined five healthy dogs and seven dogs suffering from diseases that necessitated general anesthesia for further diagnostics and treatment and that were not expected to interfere with the results of electrodiagnostic testing. By using the incremental technique to study MUNE in the cranial tibial muscle, we determined the number of motor units, the size of the compound muscle action potential, and the mean size of individual motor unit potentials of each dog as well as the mean values for each group. Moreover, we studied the correlation between these parameters. Taking the results into consideration, we addressed the difficulties and limitations of this technique. We, furthermore, pointed out possible fields of application for MUNE in canine neurology, and emphasized several aspects that future studies should focus on when applying MUNE to canine patients.