Absence of mutations in the survival motor neuron cDNA from labrador retrievers with an inherited myopathy

Noninvasive Assessment of Neuromuscular Disease in Dogs: Use of the 6-minute Walk Test to Assess Submaximal Exercise Tolerance in Dogs with Centronuclear Myopathy

Background

Noninvasive methods of quantitating exercise tolerance in dogs with neuromuscular disease are needed both for clinical and research use. The 6‐minute walk test (6MWT) has been validated as a reliable test of exercise tolerance in dogs with pulmonary and cardiac disease, but not in dogs with neuromuscular disease.

Hypothesis/Objectives

Distance walked and number of steps taken during 6MWT will differ between Labrador retriever dogs with centronuclear myopathy (CNM) and control (ie, healthy) littermates.

Animals

Eight purebred Labrador retrievers were drawn from a purpose‐bred research colony (status: 3 clear, 2 carrier, and 3 homozygous mutants for the protein tyrosine phosphatase‐like A (PTPLA) gene mutation associated with CNM).

Methods

Pilot, prospective, Case–controlled study. Researchers were blinded to disease status. Each dog was leash‐trained and acclimatized to the testing area (length, 12.8 m). At the start of testing, each animal was fitted with a pedometer, a timer was started, and dogs were allowed to walk at their own pace for 6 minutes. Distance walked and pedometer readings were recorded.

Results

Degree of paresis varied among affected dogs, and was reflected by significant differences in distance walked between CNM‐affected dogs and those with clear and carrier genotypes (P = .048). Pedometer readings did not vary according to genotype (P = .86).

Conclusions

The 6MWT appears to differentiate between the ambulatory capacity of normal and CNM‐affected dogs. Additional studies are needed to confirm this relationship in a larger number of dogs, and to evaluate the ability of the 6MWT to differentiate between dogs with variable severity of neuromuscular disease‐associated exercise intolerance.

Canine muscle cell culture and consecutive patch-clamp measurements - a new approach to characterize muscular diseases in dogs

BACKGROUND

The recognition of functional muscular disorders, (e.g. channelopathies like Myotonia) is rising in veterinary neurology. Morphologic (e.g. histology) and even genetic based studies in these diseases are not able to elucidate the functional pathomechanism. As there is a deficit of knowledge and skills considering this special task, the aim of the current pilot study was to develop a canine muscle cell culture system derived from muscle biopsies of healthy client-owned dogs, which allows sampling of the biopsies under working conditions in the daily veterinary practise.

RESULTS

Muscular biopsies from 16 dogs of different age and breed were taken during standard surgical procedures and were stored for one to three days at 4°C in a transport medium in order to simulate shipping conditions. Afterwards biopsies were professionally processed, including harvesting of satellite cells, inducing their proliferation, differentiating them into myotubes and recultivating myotubes after long-term storage in liquid nitrogen. Myogenic origin of cultured cells was determined by immunofluorescence, immunohistology and by their typical morphology after inducing differentiation. Subsequent to the differentiation into myotubes feasibility of patch-clamp recordings of voltage gated ion channels was successfully.

CONCLUSION

We have developed a canine muscle cell culture system, which allows sampling of biopsies from young and old dogs of different breeds under practical conditions. Patch clamp measurements can be carried out with the cultured myotubes demonstrating potential of these cells as source for functional research.

Evaluations of labrador retrievers with exercise-induced collapse, including response to a standardized strenuous exercise protocol

Clinical and metabolic variables were evaluated in 14 Labrador retrievers with exercise-induced collapse (EIC) before, during, and following completion of a standardized strenuous exercise protocol. Findings were compared with previously reported variables from 14 normal Labrador retrievers that participated in the same protocol. Ten of 14 dogs with EIC developed an abnormal gait during evaluation, and these dogs were significantly more tachycardic and had a more severe respiratory alkalosis after exercise compared to the normal dogs. Muscle biopsy characteristics and sequential lactate and pyruvate concentrations were normal. Genetic testing and linkage analysis excluded malignant hyperthermia as the cause of EIC. Common causes of exercise intolerance were eliminated, but the cause of collapse in EIC was not determined.

Molecular Biology for the Clinician: Understanding Current Methods

The basics of molecular biology involve the replication of deoxyribonucleic acid and its transcription and translation into proteins. Biochemical assays such as the Southern blot analysis, polymerase chain reaction (PCR), Northern blot analysis, reverse-transcriptase PCR, microarray technology, Western blot analysis, immunohistochemistry, enzyme-linked immunosorbent assay, and flow cytometry utilize various aspects of molecular biology. To understand these assays requires some basic understanding of the principles of molecular biology. This paper provides basic information on the methodology and techniques used in these assays.