Ophthalmic and cone derived electrodiagnostic findings in outbred Miniature Long-haired Dachshunds homozygous for a RPGRIP1 mutation

Objective To investigate ophthalmic and cone‐derived electrodiagnostic findings in outbred Miniature Long‐haired Dachshunds (MLHD) homozygous for a mutation in the RPGRIP1 gene previously associated with cone‐rod dystrophy 1 (cord1). Animals A total of 36 MLHD homozygous for the RPGRIP1 mutation and 23 dogs clear of the mutation (control group). Procedures The dogs underwent ophthalmic examination and photopic electroretinogram (ERG) recordings. Results None of the control dogs presented with clinical or ophthalmic signs consistent with cord1. Amongst the dogs homozygous for the mutation one presented with bilateral symmetrical total retinal atrophy. None of the other dogs in this group showed signs consistent with cord1. Photopic ERG recordings were available in 23 control dogs and 34 dogs homozygous for the mutation. Photopic a‐ and b‐waves following four light stimuli (3 cdS/m²) at a rate of 5.1 Hz were not significantly different between groups. The amplitudes of the 30 Hz flicker (128 flashes, 3 cdS/m²) response were significantly reduced in the dogs homozygous for the PRGRIP1 mutation. The difference in age between the two groups did not significantly affect the difference. Conclusion Homozygosity of the RPGRIP1 mutation does not invariably result in early onset cord1. However, cone derived ERG recordings show evidence of a reduced cone or inner retinal function in homozygous but clinically normal MLHD. Modifying genes that have yet to be identified may influence an individual dog’s risk of developing the blinding cord1 and also the age of onset and rate of progression.     

Physical therapy assessment tools to evaluate disease progression and phenotype variability in Golden Retriever muscular dystrophy

Dogs suffering from Golden Retriever muscular dystrophy (GRMD) present symptoms that are similar to human patients with Duchenne muscular dystrophy (DMD). Phenotypic variability is common in both cases and correlates with disease progression and response to therapy. Physical therapy assessment tools were used to study disease progression and assess phenotypic variability in dogs with GRMD. At 5 (T0), 9 (T1), 13 (T2) and 17 (T3) months of age, the physical features, joint ranges of motion (ROM), limb and thorax circumferences, weight and creatine kinase (CK) levels were assessed in 11 dogs with GRMD. Alterations of physical features were higher at 13 months, and different disease progression rates were observed. Passive ROM decreased until 1 year old, which was followed by a decline of elbow and tarsal ROM. Limb and thorax circumferences, which were corrected for body weight, decreased significantly between T0 and T3. These measurements can be used to evaluate disease progression in dogs with GRMD and to help discover new therapies for DMD patients.     

Detection of cone dysfunction induced by digoxin in dogs by multicolor electroretinography

It is difficult to detect discrete cone function with the present conventional electroretinography (ERG) examination. In this study, we developed contact electrodes with a built-in color (red (644 nm), green (525 nm), or blue (470 nm)) light source (color LED-electrode), and evaluated an experimental model of digoxin in the dog. First, 17 normal Beagle dogs were used to determine which electrode works well for color ERG measurement on dogs. Then, color ERG was performed on seven normal Beagle dogs at various points during a 14-day period of digoxin administration. A single daily dose of 0.0125 mg/kg/day, which is within the recommended oral maintenance dosage range for dogs, was administered orally for 2 weeks. Ophthalmic examination, measurement of plasma concentration of digoxin, and color ERG examination were performed. On first examination, amplitudes of all responses were significantly (P < 0.01) lower with the red, than with the blue and green electrodes during ERG recording. In ERG using the red electrode, the standard deviation was large. According to these preliminary results, the red electrode was not used in the experimental dog model with digoxin. In the digoxin administrated animals, no significant change was observed in the ophthalmic examination findings. The digoxin level increased steadily throughout the dosing period but was always within the therapeutic range for dogs. In rod ERG, no abnormalities were detected with any electrode. In standard combined ERG, decreased amplitude of the a-wave was detected with every electrode. In single flash cone ERG, prolongation of implicit time was detected by color ERG with the blue and green electrodes. In 30-Hz flicker ERG, decreased amplitude was detected only by color ERG with the blue electrode. The decreased amplitude and prolonged implicit time recovered after termination of digoxin administration. Cone dysfunction induced by digoxin in the dog was revealed by multicolor ERG using blue and green LED-electrodes. Multi-color ERG was useful for detecting cone type-specific dysfunction in the dog.     

Evaluation of a short interspersed nucleotide element in the 3' untranslated region of the defective dystrophin gene of dogs with muscular dystrophy.

OBJECTIVES: To determine the distribution of a 231-base pair (bp) element in the dystrophin gene 3' untranslated region (UTR) in a colony of Golden Retrievers with muscular dystrophy and other unrelated dogs and to estimate the frequency of recombination for the canine dystrophin gene. ANIMALS: 77 dogs from the Golden Retriever Muscular Dystrophy (GRMD) colony at the Murdoch Veterinary School and 30 unrelated dogs from the Murdoch University Veterinary Clinic. PROCEDURE: Samples of blood or hair from dogs were used for amplification of DNA, using primers to the canine dystrophin 3' UTR. RESULTS: The DNA from affected dogs generated a larger PCR product than that obtained from clinically normal dogs. Products were cloned and sequenced, and the difference in size was found to be attributable to a 231-bp short interspersed nucleotide element (SINE). The SINE was found in all affected dogs in the colony but not in most unaffected puppies in the colony. Eighteen of 19 dogs in the colony were heterozygous for the GRMD mutation, and 7 of 30 unrelated dogs also were heterozygous for the SINE. CONCLUSION AND CLINICAL RELEVANCE: Evidence of recombination between the GRMD mutation and the SINE was observed in only 4 dogs (2 sets of littermates) in the GRMD colony. Incidence of this SINE in a few unrelated dogs suggests that this particular insertion into the dystrophin gene may have been a recent event. The SINE in the dystrophin 3' UTR did not have an apparent influence on dystrophin mRNA concentrations.     

Assessment of the dark-adaptation time required for recovery of electroretinographic responses in dogs after fundus photography and indirect ophthalmoscopy

OBJECTIVE: To investigate the duration of dark-adaptation time required for recovery of electroretinographic responses after fundus photography or indirect ophthalmoscopy in dogs. ANIMALS: 6 dogs. PROCEDURE: Initially, scotopic-intensity series of electroretinograms (ERGs) were recorded after 20 minutes of dark adaptation. The fundus of the left eye of each dog was photographed (n = 10) or examined via indirect ophthalmoscopy for 5 minutes with moderate- (117 candela [cd]/m2) or bright-intensity (1,693 cd/m2) light; ERGs were repeated after a further 20 or 60 minutes of dark adaptation (6 procedures/dog). RESULTS: Following 20 minutes of dark adaptation after fundus photography, the b- and a-wave amplitudes were reduced in response to brighter stimuli, compared with pretest ERGs; after 60 minutes of dark adaptation, ERG amplitudes had recovered. Following 20 minutes of dark adaptation after indirect ophthalmoscopy (moderate-intensity light), significantly lower b-wave amplitudes were recorded in response to 2 of the brighter flash stimuli, compared with pretest ERGs; after 60 minutes of dark adaptation, ERG amplitudes had recovered. Following 20 minutes of dark adaptation after indirect ophthalmoscopy (bright-intensity light), all ERG amplitudes were significantly decreased and implicit times were significantly decreased at several flash intensities, compared with pretest ERGs; after 60 minutes of dark adaptation, ERG amplitudes and implicit times had returned to initial values, except for b-wave amplitudes recorded in response to dimmer stimuli. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that at least 60 minutes of dark adaptation should be allowed before ERGs are performed in dogs after fundus photography or indirect ophthalmoscopy.     

Muscular dystrophy in dogs: does the crossing of breeds influence disease phenotype?

Golden Retriever (GR) muscular dystrophy is an inherited degenerative muscle disease that provides an excellent model for Duchenne muscular dystrophy in humans. This study defined the histopathologic lesions, including the distribution of type I and II muscle fibers (FTI and FTII), in 12 dystrophic and 3 nondystrophic dogs between 7 and 15 months of age. The authors were interested in studying the influence on disease phenotype from crossing the base GR breed with Yellow Labrador Retrievers. The dystrophic dogs were divided according to breed: GRs and Golden Labrador Retrievers (GLRs). On hematoxylin and eosin staining, histopathologic lesions were more severe in GRs than GLRs. Six of eight GR muscles (75%) had a severe lesion grade (grade 3). In contrast, seven GLR muscles (87.5%) had mild lesions (grade 2), and only one had severe lesions (grade 3). Changes in fiber-type distribution were more pronounced in GRs versus GLRs. FTI:FTII ratio inversion was observed in three dystrophic GRs but only one GLR. The mean diameter of FTI and FTII was smaller in GRs and GLRs than in nondystrophic dogs (P < .01). The FTI of five GR muscles (62.5%) were larger than those of GLRs, whereas only one GLR muscle was larger (P < .05). The differential was less pronounced for FTII, with four GR muscles being larger and three GLR being larger. Observations indicate that crossing the base GR breed with Labrador Retrievers lessened the severity of the GR muscular dystrophy phenotype.     

Development of a snapback method of single-strand conformation polymorphism analysis for genotyping Golden Retrievers for the X-linked muscular dystrophy allele.

OBJECTIVE: To develop a snapback method of single-strand conformation polymorphism (SSCP) analysis for genotyping Golden Retrievers for the X-linked muscular dystrophy allele. ANIMALS: 20 Golden Retriever puppies from a colony with X-linked muscular dystrophy. PROCEDURE: DNA spanning the canine dystrophin mutation was amplified by means of a polymerase chain reaction (PCR), using a primer modified to have an additional sequence at the 5' terminus. The primer was designed so that 1 terminus of the single-stranded PCR product could anneal to the normal sequence flanking the region of the mutation in the allele but not in the mutant allele. True disease status of the dogs was determined by means of a PCR and restriction digest protocol. RESULTS: Snapback SSCP analysis allowed for accurate and unambiguous genotyping of unaffected, carrier, and affected dogs, whereas conventional SSCP analysis, using the unmodified primer, did not. Creatine kinase activities measured within 24 hours after birth were not consistent with genotype. CONCLUSION AND CLINICAL RELEVANCE: Snapback SSCP analysis provided a simple, fast, and accurate method for genotyping Golden Retrievers for the mutation known to cause X-linked muscular dystrophy.     

Electroretinography using contact lens electrode with built-in light source in dogs

Electroretinography (ERG) is an effective method for the diagnosis of retinal disease. In the dog, dependable ERG recording is difficult without the use of an expensive device like a Ganzfeld full-field stimulator. The International Society for Clinical Electrophysiology of Vision has defined the standard flash stimulus condition (SF) and evaluation of the retina using the b/a ratio in humans. In dogs, evaluation using the b/a ratio has not been reported, whereas the intensity of SF has been defined. In this study, we performed a convenient ERG recording method using a contact lens electrode with a built-in light source (LED-electrode), and confirmed SF as reported previously. ERG recordings were performed on 15 healthy beagle dogs under sedation. We performed bilateral ERG at 12 different intensities after 30 min dark adaptation. After 10 min light adaptation, we recorded single flash cone and flicker cone response using the SF determined in this study. In this study, SF of 3.0 cd/m(2)/sec (6,000 cd/m(2), 0.5 msec) resulted in b/a=2. The intensity for rod response that recorded only the b-wave was 0.0096 cd/m(2)/sec (80 cd/m(2), 0.12 msec). We could achieve ERG for each response easily and smoothly under sedation, and without general anesthesia. Using an LED-electrode, we could perform more quantitative and reproducible ERG examinations than with traditional methods. We propose that the b/a ratio is the most useful parameter in ERG reporting for evaluating retinal function.     

Diagnostic potential of natriuretic peptides in the occult phase of golden retriever muscular dystrophy cardiomyopathy

The objective of the study was to determine whether the plasma concentrations of atrial and brain natriuretic peptides (ANP and BNP, respectively) could be reliable markers of cardiac alterations during occult cardiomyopathy in Golden Retriever Muscular Dystrophy (GRMD). Fifty Golden Retrievers without any clinical or radiographic sign of heart disease were included in this study (21 GRMD dogs and 29 controls). Controls and GRMD dogs were divided into 2 subgroups according to age (< and > or =12 months old, respectively). All dogs underwent echocardiography and determination of BNP and ANP plasma concentrations by radioimmunoassay. No ventricular dilatation or dysfunction was observed in either control or GRMD dogs. ANP plasma concentration did not differ significantly between controls and GRMD dogs (mean +/- SD = 72 +/- 49 versus 58 +/- 23 pg/mL, respectively, P = .21). This finding was confirmed in both subgroups of dogs (ie, those < and > or =12 months old). In contrast, BNP plasma concentrations were significantly higher in GRMD dogs than in controls (mean +/- SD = 117 +/- 92 versus 46 +/- 22 pg/mL, respectively, P < .05). In dogs > or =12 months old, sensitivity and specificity of BNP for identifying GRMD with a cutoff of 65 pg/mL were 78 and 86%, respectively. For the same cutoff value, sensitivity dropped to 42%, whereas specificity reached 100% in dogs <12 months old. In conclusion, BNP may be a useful biochemical marker of asymptomatic cardiomyopathy. However, this peptide does not allow very early detection because its optimal discriminatory power was observed in adult dogs (ie, > or =12 months of age).     

Tissue Doppler assessment of diastolic and systolic alterations of radial and longitudinal left ventricular motions in Golden Retrievers during the preclinical phase of cardiomyopathy associated with muscular dystrophy

OBJECTIVE: To quantify radial and longitudinal left ventricular free wall (LVFW) velocities in dogs during the preclinical phase of Golden Retriever muscular dystrophy (GRMD)-associated cardiomyopathy by use of tissue Doppler imaging (TDI). ANIMALS: 9 dogs with GRMD and 6 healthy control dogs. PROCEDURE: All dogs (< 3 years old) were examined via conventional echocardiography and 2-dimensional color TDI. Myocardial velocities in the LVFW were recorded from right parasternal ventricular short-axis (radial motion) and left apical 4-chamber (longitudinal motion) views. Cardiac assessments via TDI included maximal systolic and early and late diastolic LVFW velocities in the endocardial and epicardial layers (for radial motion) and in the basal and apical segments (for longitudinal motion) (for longitudinal motion), RESULTS:-No notable ventricular dilatation or alteration of inotropism was detected in dogs with GRMD via conventional echocardiography. Compared with healthy dogs, endocardial velocities were significantly decreased in dogs with GRMD, resulting in marked decreases in radial myocardial velocity gradients during systole and early and late diastole. Similarly, basal and apical velocities were significantly decreased in systole and the former also in early diastole, resulting in significant decreases in the 2 corresponding longitudinal myocardial velocity gradients. The radial epicardial and longitudinal late diastolic velocities were comparable in the 2 groups. CONCLUSION AND CLINICAL RELEVANCE: Results indicated that GRMD-associated cardiomyopathy in dogs is associated with early marked dysfunction of both radial and longitudinal LVFW motions. These combined regional myocardial abnormalities might be useful criteria for detection of dilated cardiomyopathy at the preclinical stage of the disease in dogs.     

Clinical findings in early onset cone-rod dystrophy in the Standard Wire-haired Dachshund

OBJECTIVE: To describe the clinical findings and the age of onset of cone-rod dystrophy (crd) in the Standard Wire-haired Dachshund (SWHD) and to evaluate which clinical tests could be used to obtain a reliable diagnosis. ANIMALS: Sixty-eight SWHD and SWHD-derived dogs were used, including 23 affected with crd and 45 controls, respectively. PROCEDURES: The dogs were subjected to behavioral testing, examination of pupillary light reflexes (PLRs), indirect ophthalmoscopy and bilateral full field electroretinography (ERG). RESULTS: The majority of affected puppies (5-10 weeks) displayed pin-point sized pupils upon examination with focal light. All dogs in the control group, except one, displayed normal PLRs upon examination. In all crd-affected dogs there was a great variation both in age of onset and in clinical appearance of retinal changes upon fundoscopy. Two siblings displayed panretinal degeneration at the age of 10 months while other affected dogs showed early changes at the age of 3 years. Generalized bilateral retinal atrophy was the end stage of the disease. The maze test revealed no obvious differences among affected and unaffected groups. ERG recordings showed only slightly reduced rod, and mixed rod-cone responses, but severely reduced cone single flash a- and b-wave amplitudes, and cone flicker amplitudes were observed in all affected dogs. CONCLUSION: Presence of pin-point sized pupils in young SWHDs was found to be an important indicator of early onset crd. Fundoscopic changes and progression of disease at later stages resembled those previously described in the majority of progressive retinal atrophies in dog. ERG was found to be the most reliable diagnostic procedure to clinically diagnose crd in the SWHD.     

Characterization of the normal dark adaptation curve of the horse

Objective The goal of this work is to study the dark adaptation curve of the normal horse electroretinogram (ERG). Procedures The electroretinographic responses were recorded from six healthy female ponies using a contact lens electrode and a mini‐Ganzfeld electroretinographic unit. The horses were sedated intravenously with detomidine, an auriculopalpebral nerve block was then performed, and the pupil was fully dilated. The ERG was recorded in response to a low intensity light stimulus (30 mcd.s/m²) that was given at times (T) T = 5, 10, 15, 20, 25, 30, 40, 50, and 60 min of dark adaptation. Off‐line analysis of the ERG was then performed. Results Mean b‐wave amplitude of the full‐field ERG increased continuously from 5 to 25 min of dark adaptation. The b‐wave amplitude peaked at T = 25, however, there was no statistical significance between T = 20 and T = 25. The b‐wave amplitude then remained elevated with no significant changes until the end of the study at T = 60 (P > 0.49). The b‐wave implicit time increased continuously between T = 5 and T = 20, then gradually decreased until T = 60. No distinct a‐wave was observed during the testing time. Conclusions Evaluation of horse rod function or combined rod/cone function by means of full‐field ERG should be performed after a minimum 20 min of dark adaptation.     

Retinal degeneration in nine Swedish Jämthund dogs

The Jämthund is the fourth most common breed in Sweden with approximately 1600 pups registered each year. Although it has been known that some adult dogs go blind, so they cannot hunt, the Jämthund dog has historically not been screened for hereditary eye diseases. This report describes nine Swedish Jämthund dogs with retinal degeneration. These dogs represent all Jämthund dogs diagnosed with progressive retinal atrophy (PRA) by the Swedish Eye Panel and registered with the Swedish Kennel Club from January 1998 to September 2008. The dogs were examined with indirect opthalmoscopy and slitlamp biomicroscopy. Additionally, electroretinograms (ERGs) following ECVO guidelines were performed in two dogs (one affected and one normal) and the eyes from three affected dogs were examined by light‐microscopy postmortem. Typical findings were bilateral symmetric generalized retinal degeneration with tapetal hyper‐reflectivity, attenuation of blood vessels and pigment clumping in the nontapetal fundus. These retinal findings progressed with time in two dogs after re‐examination. Visual impairment, especially under dim light conditions, was observed in the affected dogs. ERG from one affected dog showed profoundly reduced rod responses, whereas cone responses were better preserved. Microscopic changes in the eyes from three dogs were characterized by a severe diffuse predominantly outer retinal degeneration and atrophy. Re‐sequencing of the prcd‐gene for eight of the nine investigated dogs revealed that none of the individuals carried disease allele that has been associated with prcd‐PRA in other breeds. In conclusion, ophthalmoscopic, electroretinographic, and light‐microscopic alterations observed in nine Jämthund dogs were compatible with PRA. The prcd mutation was excluded as a cause of this retinopathy.     

RADIOGRAPHIC FEATURES OF GOLDEN RETRIEVER MUSCULAR DYSTROPHY

Golden Retriever muscular dystrophy is an inherited, degenerative myopathy due to the absence of dystrophin and is used as a model of Duchenne muscular dystrophy of young boys. This report describes the radiographic abnormalities of Golden Retriever muscular dystrophy in 26 dogs. The thoracic abnormalities included diaphragmatic asymmetry (18/26), diaphragmatic undulation (18/26), and gastro-esophageal hiatal hernia (6/26). Pelvic abnormalities included narrowing of the body of the ilia (14/19), ventral deviation and curvature of the tuber ischii (14/19), elongation of the obturator foramen with a decrease in opacity of the surrounding bone (12/19), and lateral flaring of the wings of the ilia (12/19). Abdominal abnormalities consisted of hepatomegaly (14/22) and poor serosal detail (12/22). The unique thoracic abnormalities were a consistent finding in affected Golden Retriever muscular dystrophy dogs. The diagnosis of muscular dystrophy should be included in the differential list if the combination of diaphragm undulation and asymmetry, and gastro-esophageal hiatal hernia are identified. These diaphragmatic abnormalities are related to hypertrophy and hyperplasia of the diaphragm. Additionally, the skeletal changes of pelvic tilt, elongation of the pelvis, widening of the obturator foramina and thinning of the ischiatic tables appear to be specific to Golden Retriever muscular dystrophy in dogs. These pelvic abnormalities are most likely secondary to bone remodeling associated with the progressive skeletal myopathy and subsequent contracture/fibrosis.     

Bartonella DNA in the blood and lymph nodes of Golden Retrievers with lymphoma and in healthy controls

BACKGROUND: Although lymphoma is the most common neoplastic process reported in dogs, its precise etiology is unknown. Golden Retrievers are more likely to develop lymphoma, suggesting a breed predisposition; however, other factors, including environment, immunity, and infection, are likely contributors to oncogenesis. HYPOTHESIS: We hypothesized that the development of lymphoma in Golden Retrievers may be associated with vector-borne infections, specifically Bartonella, Anaplasma, or Ehrlichia species infections. ANIMALS: Golden Retrievers with lymphoma and healthy Golden Retrievers from across the United States were recruited for study participation. METHODS: A matched, case-control study was performed to determine the association of lymphoma and the presence of Bartonella, Anaplasma, and Ehrlichia species in serum, blood, and lymph node aspirates. RESULTS: Using PCR analyses and DNA sequencing, single and coinfections with Bartonella henselae, Bartonella elizabethae, Bartonella quintana, and/or Bartonella vinsonii (berkhoffii) were detected in the blood and lymph node aspirates of Golden Retrievers with lymphoma (5/28 dogs, 18%) and in healthy Golden Retrievers (10/56 dogs, 18%); no Anaplasma or Ehrlichia DNA was detected in any dog. When compared with dogs with lymphoma, a higher (P <.001) proportion of healthy Golden Retrievers were receiving monthly acaricide treatments (2.6 times higher). CONCLUSIONS AND CLINICAL IMPORTANCE: Bartonella DNA can be detected in blood and lymph nodes; importantly, in this report, Bartonella was detected in the same proportion of clinically healthy dogs and dogs with lymphoma. Longitudinal studies should be conducted to determine the mode of transmission of Bartonella in dogs, whether lymphatic infection is persistent, or whether these bacteria may contribute to the development of lymphoma.     

The DC-recorded dog electroretinogram in ketamine-medetomidine anaesthesia

A new selective alpha 2-adre-noreceptor agonist, medetomidine hydrochloride was combined with low dosage ketamine hydrochloride and vecuronium bromide for d.c. (direct current) recordings of fast electroretinographic (ERG) components in nine ophthalmoscopically healthy dark adapted dogs. The dogs were tracheally intubated and manually ventilated. They were given full field single flash stimuli of different intensities starting with near b-wave threshold blue light (tests 1-3), followed by white light (tests 4-6) and 30 Hz photopic flicker (test 7). The a- and b-wave amplitudes and flicker responses were measured from the base line. The latencies were measured from the stimulus moment to the highest point of the different waves.Statistical analysis of results gave individual differencies which had a good constancy. This showed that the dogs had an individual ERG profile according to the standardized method. The latencies varied very little as expected, but the amplitudes differed individually and showed a good constancy as seen by reproducibility tests made nine to ten days later on three of the dogs’ ipsilateral eyes. The combination of drugs used in this study was considered suitable for short term (10-12 minutes) stable d.c.–ERG recordings in dogs as the rod and cone responses had higher amplitudes when compared to an identical examination made with other anaesthetic combinations on the same dogs.Involuntary eye movements and other involuntary muscular activity caused by ketamine in dogs were negligible when using medetomidine premedication and was completely absent when using vecuronium.The anaesthetic method described can be recommended for ambulatory ERG recordings in dogs because of the above mentioned advantages.     

Clinical electroretinography in the dog. Part 3]

In this last part the preparation of the patient for the ERG is shown. Anesthesia, positioning, and retrobulbar injection technique are discussed. The protocol for recording the ERG is presented. The dog is dark adapted for 30 minutes. The level of adaptation is examined using a single flash of dim red light at various times. Rods and cones are stimulated separately by scotopically balanced red and blue flashes. After a single flash of bright white light the rods and cones are studied with flicker trains at 5, 12.5, 15 and 30 Hz. During dark adaptation the maximum b-wave amplitude increased from 13.8 +/- 8.4 microV to 49.3 +/- 16.3 microV. Bright white light stimuli resulted in b-wave amplitudes of 167.7 +/- 75.3 microV. There were always 6 oscillatory potentials visible on the b-wave. Scotopically balanced stimuli produced b-waves of 104 microV (red) and 116 microV (blue). It was found that older dogs had reduced b-wave amplitudes and longer peak times than younger dogs. The most common artefacts in electroretinography are discussed.     

The prevalence of medial coronoid process disease is high in lame large breed dogs and quantitative radiographic assessments contribute to the diagnosis

Medial coronoid process disease is a common leading cause of thoracic limb lameness in dogs. Computed tomography and arthroscopy are superior to radiography to diagnose medial coronoid process disease, however, radiography remains the most available diagnostic imaging modality in veterinary practice. Objectives of this retrospective observational study were to describe the prevalence of medial coronoid process disease in lame large breed dogs and apply a novel method for quantifying the radiographic changes associated with medial coronoid process and subtrochlear‐ulnar region in Labrador and Golden Retrievers with confirmed medial coronoid process disease. Purebred Labrador and Golden Retrievers (n = 143, 206 elbows) without and with confirmed medial coronoid process disease were included. The prevalence of medial coronoid process disease in lame large breed dogs was calculated. Mediolateral and craniocaudal radiographs of elbows were analyzed to assess the medial coronoid process length and morphology, and subtrochlear‐ulnar width. Mean grayscale value was calculated for radial and subtrochlear‐ulnar zones. The prevalence of medial coronoid process disease was 20.8%. Labrador and Golden Retrievers were the most affected purebred dogs (29.6%). Elbows with confirmed medial coronoid process disease had short (P < 0.0001) and deformed (～95%) medial coronoid process, with associated medial coronoid process osteophytosis (7.5%). Subtrochlear‐ulnar sclerosis was evidenced in ～96% of diseased elbows, with a significant increase (P < 0.0001) in subtrochlear‐ulnar width and standardized grayscale value. Radial grayscale value did not differ between groups. Periarticular osteophytosis was identified in 51.4% of elbows with medial coronoid process disease. Medial coronoid process length and morphology, and subtrochlear‐ulnar width and standardized grayscale value varied significantly in dogs with confirmed medial coronoid process disease compared to controls. Findings indicated that medial coronoid process disease has a high prevalence in lame large breed dogs and that quantitative radiographic assessments can contribute to the diagnosis.     

Analysis of a deletion in the nephronophthisis 4 gene in different dog breeds

Cone‐rod dystrophy is a progressive inherited retinal degenerative disorder that occurs in humans and dogs. The deletion in the nephronophthisis 4 (NPHP4) gene was established as a causative mutation in standard wire‐haired Dachshunds. We analyzed all varieties of Dachshunds from the Czech Republic and five other dog breeds and found that the deletion in the NPHP4 (in heterozygous state) is present not only in standard‐, but also in miniature wire‐haired Dachshunds, but not in other varieties of Dachshunds or in other breeds.     

Hereditary spectrin deficiency in Golden Retriever dogs

Spectrin deficiency with increased erythrocyte osmotic fragility (OF) is a hallmark of hereditary spherocytosis, which is the most common congenital hemolytic anemia in humans of northern European ancestry. A radioimmunoassay revealed that erythrocyte spectrin concentration was 50-65% of normal in 5 adult Golden Retriever dogs, which had recovered from hemolytic anemia but whose OF had persistently remained increased. OF also was increased and spectrin concentration was decreased (60-73%) in 10 dogs of an apparently healthy family of 19 Golden Retrievers related to a proband. Pedigree analysis revealed autosomal dominant inheritance. In addition, OF was increased in 23 (17%) of 134 randomly chosen Golden Retrievers with nonhematologic diseases. In these Golden Retrievers, the spectrin concentration was decreased in 5 dogs with increased OF and within the reference range in 6 dogs with normal OF, indicating that in this population spectrin deficiency and increased OF are highly associated (P < .002). Considering these patients a representative sample of the Golden Retriever population in the Netherlands, spectrin deficiency may occur in 11.2-24.6% of Dutch Golden Retrievers (confidence level = 0.95). In blood smears, spherocytes were recognized only in dogs with immune-mediated anemia. At scanning electron microscopy, blood from spectrin-deficient Golden Retrievers showed slight crenation when fixed freshly but abundant echinospherocytes after 24 hours of incubation. We conclude that occult autosomal dominant spectrin deficiency occurs in dogs and is frequent in Dutch Golden Retrievers. It is not clear whether spectrin deficiency in Golden Retrievers may result in hemolytic anemia, as in humans.