A missense mutation in MYO7A is associated with bilateral deafness and vestibular dysfunction in the Doberman pinscher breed.

Bilateral deafness with concurrent vestibular dysfunction was first reported in the Doberman pinscher in 1980. Here, we identify a coding mutation in the MYO7A gene that is perfectly associated with the disorder. The lack of visual deficits in affected dogs suggests that, like rodents but unlike humans, MYO7A is not required for retinal function. DNA testing of the mutation will enable dog breeders to manage the incidence of this genetic defect.

La surdité bilatérale avec dysfonctionnement vestibulaire concomitant a été rapporté pour la première fois chez le Doberman pinscher en 1980. Ici nous identifions une mutation codante dans le gène MYO7A qui est associée parfaitement avec cette condition. L'absence de défaut rétinien chez les chiens atteints suggère que, comme chez les rongeurs mais contrairement aux humains, MYO7A n'est pas requis pour la fonction rétinienne. Les tests d'ADN pour la mutation vont permettre aux éleveurs de chiens de gérer l'incidence de ce défaut génétique.(Traduit par Docteur Serge Messier).

Variation in genes related to cochlear biology is strongly associated with adult-onset deafness in border collies.

Domestic dogs can suffer from hearing losses that can have profound impacts on working ability and quality of life. We have identified a type of adult-onset hearing loss in Border Collies that appears to have a genetic cause, with an earlier age of onset (3-5 years) than typically expected for aging dogs (8-10 years). Studying this complex trait within pure breeds of dog may greatly increase our ability to identify genomic regions associated with risk of hearing impairment in dogs and in humans. We performed a genome-wide association study (GWAS) to detect loci underlying adult-onset deafness in a sample of 20 affected and 28 control Border Collies. We identified a region on canine chromosome 6 that demonstrates extended support for association surrounding SNP Chr6.25819273 (p-value = 1.09 × 10(-13)). To further localize disease-associated variants, targeted next-generation sequencing (NGS) of one affected and two unaffected dogs was performed. Through additional validation based on targeted genotyping of additional cases (n = 23 total) and controls (n = 101 total) and an independent replication cohort of 16 cases and 265 controls, we identified variants in USP31 that were strongly associated with adult-onset deafness in Border Collies, suggesting the involvement of the NF-κB pathway. We found additional support for involvement of RBBP6, which is critical for cochlear development. These findings highlight the utility of GWAS-guided fine-mapping of genetic loci using targeted NGS to study hereditary disorders of the domestic dog that may be analogous to human disorders.

Traumatic neuroma in continuity injury model in rodents.

Traumatic neuroma in continuity (NIC) results in profound neurological deficits, and its management poses the most challenging problem to peripheral nerve surgeons today. The absence of a clinically relevant experimental model continues to handicap our ability to investigate ways of better diagnosis and treatment for these disabling injuries. Various injury techniques were tested on Lewis rat sciatic nerves. Optimal experimental injuries that consistently resulted in NIC combined both intense focal compression and traction forces. Nerves were harvested at 0, 5, 13, 21, and 65 days for histological examination. Skilled locomotion and ground reaction force (GRF) analysis were performed up to 9 weeks on the experimental (n=6) and crush-control injuries (n=5). Focal widening, disruption of endoneurium and perineurium with aberrant intra- and extrafascicular axonal regeneration and progressive fibrosis was consistently demonstrated in 14 of 14 nerves with refined experimental injuries. At 8 weeks, experimental animals displayed a significantly greater slip ratio in both skilled locomotor assessments, compared to nerve crush animals (p<0.01). GRFs of the crush- injured animals showed earlier improvement compared to the experimental animals, whose overall GRF patterns failed to recover as well as the crush group. We have demonstrated histological features and poor functional recovery consistent with NIC formation in a rat model. The injury mechanism employed combines traction and compression forces akin to the physical forces at play in clinical nerve injuries. This model may serve as a tool to help diagnose this injury earlier and to develop intervention strategies to improve patient outcomes.

Dose and duration of nerve growth factor (NGF) administration determine the extent of behavioral recovery following peripheral nerve injury in the rat.

Nerve growth factor (NGF) has been previously shown to support neuron survival and direct neurite outgrowth in vitro, and to enhance axonal regeneration in vivo. However, a systematic analysis of NGF dose and dose duration on behavioral recovery following peripheral nerve injury in rodents has not been previously investigated. Here, we show that NGF promotes a bell shaped dose-response, with an optimal threshold effect occurring at 800 pg/µl. High dose NGF inhibited regeneration. However, this effect could be reversed through functional blockade of p75 receptors, thus implicating these receptors as mediators of the inhibitory response. Longer term evaluation showed that animals administered NGF at 80 ng/day for 3 weeks had greater sensorimotor recovery compared to all other treatment groups. These animals made significantly fewer errors during skilled locomotion, and displayed both increased vertical and fore-aft ground reaction forces during flat surface locomotion. Furthermore, terminal electrophysiological and myological assessments (EMG, wet gastrocnemius muscle weights) corroborated the behavioral data. Overall, these data support the hypothesis that both appropriate dose and duration of NGF are important determinants of behavioral recovery following nerve injury in the rat.

Kinematics and ground reaction force determination: a demonstration quantifying locomotor abilities of young adult, middle-aged, and geriatric rats.

Behavior, in its broadest definition, can be defined as the motor manifestation of physiologic processes. As such, all behaviors manifest through the motor system. In the fields of neuroscience and orthopedics, locomotion is a commonly evaluated behavior for a variety of disease models. For example, locomotor recovery after traumatic injury to the nervous system is one of the most commonly evaluated behaviors . Though locomotion can be evaluated using a variety of endpoint measurements (e.g. time taken to complete a locomotor task, etc), semiquantitative kinematic measures (e.g. ordinal rating scales (e.g. Basso Beattie and Bresnahan locomotor (BBB) rating scale, etc)) and surrogate measures of behaviour (e.g. muscle force, nerve conduction velocity, etc), only kinetics (force measurements) and kinematics (measurements of body segments in space) provide a detailed description of the strategy by which an animal is able to locomote . Though not new, kinematic and kinetic measurements of locomoting rodents is now more readily accessible due to the availability of commercially available equipment designed for this purpose. Importantly, however, experimenters need to be very familiar with theory of biomechanical analyses and understand the benefits and limitations of these forms of analyses prior to embarking on what will become a relatively labor-intensive study. The present paper aims to describe a method for collecting kinematic and ground reaction force data using commercially available equipment. Details of equipment and apparatus set-up, pre-training of animals, inclusion and exclusion criteria of acceptable runs, and methods for collecting the data are described. We illustrate the utility of this behavioral analysis technique by describing the kinematics and kinetics of strain-matched young adult, middle-aged, and geriatric rats.

Spinal cord injury II: Prognostic indicators, standards of care, and clinical trials.

This is the second of a 2-part review of spinal cord injury. The focus herein is to highlight recent findings regarding prognostic indicators used for spinal cord injury (SCI) in dogs, promote an awareness of the current recommendations of standard of care for traumatic spinal cord injury in veterinary medicine, and highlight the findings of clinical trials of therapies for spinal cord injury in dogs. This 2-part review provides information that will assist general and specialty veterinary practitioners in evidence-based veterinary medical practice in an area that has become particularly specialized.

Spinal cord injury I: A synopsis of the basic science.

Substantial knowledge has been gained in the pathological findings following naturally occurring spinal cord injury (SCI) in dogs and cats. The molecular mechanisms involved in failure of neural regeneration within the central nervous system, potential therapeutics including cellular transplantation therapy, neural plasticity, and prognostic indicators of recovery from SCI have been studied. This 2-part review summarizes 1) basic science perspectives regarding treating and curing spinal cord injury, 2) recent studies that shed light on prognosis and recovery from SCI, 3) current thinking regarding standards of care for dogs with SCI, 4) experimental approaches in the laboratory setting, and 5) current clinical trials being conducted in veterinary medicine. Part I presents timely information on the pathophysiology of spinal cord injury, challenges associated with promoting regeneration of neurons of the central nervous system, and experimental approaches aimed at developing treatments for spinal cord injury.

Behavioural and anatomical analysis of selective tibial nerve branch transfer to the deep peroneal nerve in the rat.

Nerve transfer procedures involving the repair of a distal denervated nerve element with that of a foreign proximal nerve have become increasingly popular for clinical nerve repair as a surgical alternative to autologous nerve grafting. However, the functional outcomes and the central plasticity for these procedures remain poorly defined, particularly for a clinically relevant rodent model of hindlimb nerve transfer. We therefore evaluated the effect of selective tibial branch nerve transfer on behavioural recovery in animals following acute transection of the deep peroneal nerve. The results indicate that not only can hindlimb nerve transfers be successfully accomplished in a rat model but that these animals display a return of skilled locomotor function on a par with animals that underwent direct deep peroneal nerve repair (the current gold standard). At 2 months, ground reaction force analysis demonstrated that partial restoration of braking forces occurred in the nerve transfer group, whereas the direct repair group had fully restored these forces to similar to baseline levels. Ankle kinematic analysis revealed that only animals in the direct repair group significantly recovered flexion during the step cycle, indicating a recovery of surgically induced foot drop. Terminal electrophysiological and myological assessments demonstrated similar levels of reinnervation, whereas retrograde labelling studies confirmed that the peroneal nerve-innervated muscles were innervated by neurons from the tibial nerve pool in the nerve transfer group. Our results demonstrate a task-dependent recovery process, where skilled locomotor recovery is similar between nerve transfer and direct repair animals, whereas flat surface locomotion is significantly better in direct repair animals.

Lafora disease as a cause of visually exacerbated myoclonic attacks in a dog.

An 8-year-old, castrated male, miniature wire-haired dachshund was presented with a 4-month history of intermittent facial twitching (myoclonus). The myoclonic episodes progressed over a 16-month period. Generalized seizure activity was infrequent. Clinical examination revealed visually stimulated myoclonus. Response to therapy with antiepileptic drugs was equivocal. Genetic testing identified the dog as being affected by Lafora disease.

Dorsolateral cervical spinal injury differentially affects forelimb and hindlimb action in rats.

In experimental spinal injury studies, damage to the dorsal half of the spinal cord is common but the behavioural effects of damage to specific pathways in the dorsal cord have been less well investigated. We performed bilateral transection of the dorsolateral spinal funiculus (DLF) on 12 Long-Evans rats at the third cervical spinal segment. We quantified overground locomotion by measuring ground reaction forces, step timing and step distances as animals moved unrestrained. We also assessed skilled locomotion by measuring footslip errors made while the animals crossed horizontal ladders, and examined paw usage in a cylinder exploration task and during a skilled reaching task. Ground reaction forces revealed that rats with bilateral DLF lesions moved with a symmetrical gait, characterized mainly by altered forces exerted by the hindlimbs, delayed onset of hindlimb stance, and understepping of the hindlimbs relative to the forelimbs. These alterations in overground locomotion were subtle but were nevertheless consistent between animals and persisted throughout the 6-week recovery period. During ladder crossing, rats with DLF lesions made more footslip errors with the hindlimbs after surgery than before. Spontaneous forelimb usage during exploration was not affected by DLF axotomy but lesioned animals were less successful during skilled reaching. This is the first study which describes preferentially altered hindlimb use during overground locomotion after cervical DLF transections. We discuss these findings in relation to previous work and to the possible contributions of different ascending and descending pathways in the DLF to locomotion and skilled movements in rats.

Estrogen reduces the severity of autonomic dysfunction in spinal cord-injured male mice.

Autonomic dysreflexia is an autonomic behavioural condition that manifests after spinal cord injury (SCI) and is characterized by acute, episodic hypertension following afferent stimulation below the level of the injury. Common triggers of autonomic dysreflexia include colorectal distension (CRD), and various somatic stimuli. The development of autonomic dysreflexia is dependent, in part, upon the degree of intraspinal inflammation and the resultant spinal neuroplastic changes that occur following SCI. 17beta-estradiol (E) has neuroprotective, anti-inflammatory and smooth muscle relaxant properties, and is therefore a candidate drug for the treatment and/or prevention of autonomic dysreflexia. Autonomic dysreflexia was assessed in adult male mice treated with E. We investigated whether E could be acting centrally by altering: (1) the size of the small diameter primary afferent arbor, (2) the degree of microglia/macrophage infiltration at the site of the injury, or (3) the amount of fibrous scarring present at the injury site. To determine whether E could be working through uncoupling protein-2 (UCP-2), a protein involved with inflammation and regulated by estrogen in some tissues, autonomic dysreflexia was assessed in E-treated adult male mice lacking UCP-2 (UCP-2 KO). 17beta-estradiol was equipotent at reducing autonomic dysreflexia in both UCP-2 KO and WT mice following CRD but not tail pinch. We have shown that E reduces autonomic dysreflexic responses to visceral but not somatic stimulation in male mice independent of the size of the primary afferent arbour, the degree of chronic inflammation, and the presence of UCP-2.

Brainstem auditory evoked responses and ophthalmic findings in llamas and alpacas in Eastern Canada.

Seventeen llamas and 23 alpacas of various coat and iris colors were evaluated for: (1) deafness by using brainstem auditory evoked response testing; and (2) for ocular abnormalities via complete ophthalmic examination. No animals were deaf. The most common ocular abnormalities noted were iris-to-iris persistent pupillary membranes and incipient cataracts.

Intracranial meningioma causing internal ophthalmoparesis in a dog.

A 10-year-old, spayed female, Irish water spaniel was presented with a 2-week history of anisocoria characterized by mydriasis of the right eye compared to the left eye in ambient light. Ophthalmic and neurological examinations, combined with pharmacological testing, identified a disease process affecting the right parasympathetic nucleus of cranial nerve 3 (CN III) and/or the parasympathetic component of CN III. Magnetic resonance imaging (MRI) identified a mass involving the right midbrain and extending caudally to the rostral border of the medulla oblongata. The dog became comatose within 12 h following MRI and was euthanized. Histopathology identified the intracranial mass as a meningioma.

Sensorimotor behaviour following incomplete cervical spinal cord injury in the rat.

Rats are one of the most commonly used species for spinal cord injury research. Since the advent of the Basso, Beattie, Bresnahan (BBB) locomotor rating scale, the majority of spinal cord injury research relies upon evaluating locomotor behaviour in thoracic spinal cord injury rat models. Slightly more than 50% of all traumatic spinal cord injuries in humans, however, occur at the level of the cervical spinal cord. Further, therapies aimed at thoracic spinal cord injuries may not be directly transferable to cervical spinal cord injuries. This could be due to (1) differences in distance between the cell bodies of injured axons and the injury site and (2) because some behaviours (e.g. stepping movements) used to evaluate the therapeutic potential of a given treatment are governed primarily by intraspinal neuronal circuitry while other behaviours (e.g. skilled reaching) require more sophisticated conscious integration of the sensorimotor system. Consequently, there is a need to develop and use experimental cervical spinal cord injury models and understand the behavioural characteristics of such models. The present review highlights the sensorimotor abilities of cervical spinal cord-injured rats, including both forelimb, hind limb, and whole body behaviours. We also provide insight into the neuroanatomic substrates important for performing a given behaviour, information which may prove essential in the development of site-directed therapeutic strategies.

Keratoconjunctival effects of diabetes mellitus in dogs.

OBJECTIVES: To compare Schirmer tear test (STT) values, corneal sensitivity, tear film break up times (TFBUTs), and tear glucose concentrations in relation to conjunctival microflora, and conjunctival cytologic and histologic findings among diabetic cataractous, nondiabetic cataractous, and nondiabetic noncataractous dogs. Procedures Fifteen dogs in each category underwent neuro-ophthalmic examination; aerobic, anaerobic and fungal conjunctival cultures; assessment of corneal touch threshold (CTT), STT, tear glucose, TFBUT; and conjunctival cytology and histology (in certain cases only). Degree of cataract and uveitis were critically graded. Glycemic control was estimated using serum fructosamine and glycosylated hemoglobin. RESULTS: STT values were significantly lower in diabetic cataractous than nondiabetic noncataractous dogs. CTT of diabetic cataractous dogs was significantly lower than that of nondiabetic noncataractous dogs. Mean TFBUTs were significantly less in diabetic cataractous dogs than nondiabetic cataractous and nondiabetic noncataractous dogs. Tear glucose concentrations were significantly higher in diabetic cataractous dogs than nondiabetic cataractous and nondiabetic noncataractous dogs. Conjunctival microbial isolates did not differ among groups. There were no significant differences in degree of cataract or uveitis between diabetic cataractous and nondiabetic cataractous groups. There was mild submucosal inflammatory infiltrate in conjunctival specimens from diabetic dogs. Conjunctival epithelial dysplasia and/or squamous metaplasia was/were detected in conjunctival biopsies of 5/7 diabetic dogs. Reductions in conjunctival goblet cell (GC) densities were noted in 4/7 diabetic dogs; there were no significant differences in mean GC densities among the three groups. CONCLUSIONS: Diabetic cataractous dogs have significantly altered keratoconjunctival characteristics compared to nondiabetic cataractous and nondiabetic noncataractous dogs.

Course of motor recovery following ventrolateral spinal cord injury in the rat.

The purpose of this study was to determine the importance of the pathways running in the ventrolateral spinal funiculus for overground locomotion in adult, freely behaving rats. Left-sided ventrolateral cervical spinal cord injury was performed in adult female Long-Evans rats. The behavioural abilities of these animals were analyzed at 2 days, and weekly for up to 5.5 weeks following spinal cord injury. Behavioural testing consisted of Von Frey filament testing, ladder walking, a paw usage task, and the assessment of ground reaction forces during unrestrained trotting. Animals with injury to the left ventrolateral cervical spinal cord did not develop enhanced sensitivity to pedal mechanical stimulation. At 2 days following injury, animals had impaired skilled locomotion as indicated by increased number of footslips during ladder walking. At 2 days, these animals also used both limbs together more often for support while rearing, while using the forelimb ipsilateral to the injury less than did uninjured animals. Ground reaction force determination revealed that animals tend to bear less weight on the forelimb and hindlimb ipsilateral to the spinal cord injury 2 days after injury. All animals recovered normal or near normal sensorimotor abilities although subtle asymmetries in ground reaction forces were detectable at 5.5 weeks following spinal cord injury. These results suggest that axons in the ventrolateral spinal funiculi contribute to limb movements during exploration and locomotion but their roles can be served by other pathways after ventrolateral spinal injury.