Retinal dysplasia has been documented in many breeds of dogs. It has recently been hypothesized that Miniature Schnauzer dogs affected with retinal dysplasia and associated persistent hyperplastic primary vitreous have a decreased amount of Tfam and several mtDNA transcripts in the retina and RPE. Affected dogs were also hypothesized to have a decrease in leukocyte mtDNA compared to normal dogs. Additionally, using electron microscopy, these dogs were hypothesized to having decreased mitochondrial numbers and size with altered morphology in multiple tissues, including neutrophils. Due to these recent discoveries in this breed it has been proposed that retinal dysplasia could be the result of an altered energy supply to the retina and RPE. The objective of this study was to further investigate the pathogenesis of retinal dysplasia in the Miniature Schnauzer and English Springer Spaniel dog.<p> The hypothesis of an altered Tfam gene sequence in affected Miniature Schnauzer dogs leading to a decreased amount of Tfam transcript in the retina and RPE was tested by amplifying, cloning and sequencing the coding, 5 and 3non-coding regions, and intron 1 of the Tfam gene from affected and normal Miniature Schnauzer dogs. Using transmission electron microscopy, affected and normal lymphocyte mitochondria were also objectively measured and quantified in this breed along with mitochondrial morphology assessment. In the English Springer Spaniel dog, the hypothesis of a decreased amount of leukocyte mtDNA in affected dogs was tested using real-time PCR. In addition, using transmission electron microscopy, affected and normal lymphocyte mitochondria were objectively measured and quantified in this breed with mitochondrial morphology assessment.<p> Sequencing of the particular regions of the Miniature Schnauzer Tfam gene revealed no significant nucleotide changes between affected and normal dogs. Evaluation of lymphocyte mitochondrial size, number and morphology also revealed no significant differences between the two groups. In the English Springer Spaniel dog a relative decrease in leukocyte mtDNA did not exist in dogs affected with retinal dysplasia. Furthermore, evaluation of affected English Springer Spaniel dog lymphocyte mitochondria revealed no significant differences in mitochondrial number, surface area or morphology when compared to normal English Springer Spaniel dogs.<p> To conclude, we failed to demonstrate a mutation in the areas of the Tfam gene sequenced in Miniature Schnauzers affected with retinal dysplasia and associated persistent hyperplastic primary vitreous. In contrast to previous findings of decreased leukocyte mtDNA in the affected Miniature Schnauzer dog, no evidence was found to support a relative decrease in leukocyte mtDNA in English Springer Spaniel dogs affected with retinal dysplasia. Furthermore, the hypothesis of altered mitochondrial size, number and morphology in affected dogs is not supported by this study. Further evaluation of mitochondria, mtDNA and mitochondrial gene expression within age-matched retina and RPE of Miniature Schnauzer and English Springer Spaniel dogs is necessary to determine if mitochondria and altered energy supply play a role in the pathogenesis of retinal dysplasia in these breeds.

Retinal dysplasia has been documented in many breeds of dogs. It has recently been hypothesized that Miniature Schnauzer dogs affected with retinal dysplasia and associated persistent hyperplastic primary vitreous have a decreased amount of Tfam and several mtDNA transcripts in the retina and RPE. Affected dogs were also hypothesized to have a decrease in leukocyte mtDNA compared to normal dogs. Additionally, using electron microscopy, these dogs were hypothesized to having decreased mitochondrial numbers and size with altered morphology in multiple tissues, including neutrophils. Due to these recent discoveries in this breed it has been proposed that retinal dysplasia could be the result of an altered energy supply to the retina and RPE. The objective of this study was to further investigate the pathogenesis of retinal dysplasia in the Miniature Schnauzer and English Springer Spaniel dog.<p> The hypothesis of an altered Tfam gene sequence in affected Miniature Schnauzer dogs leading to a decreased amount of Tfam transcript in the retina and RPE was tested by amplifying, cloning and sequencing the coding, 5 and 3non-coding regions, and intron 1 of the Tfam gene from affected and normal Miniature Schnauzer dogs. Using transmission electron microscopy, affected and normal lymphocyte mitochondria were also objectively measured and quantified in this breed along with mitochondrial morphology assessment. In the English Springer Spaniel dog, the hypothesis of a decreased amount of leukocyte mtDNA in affected dogs was tested using real-time PCR. In addition, using transmission electron microscopy, affected and normal lymphocyte mitochondria were objectively measured and quantified in this breed with mitochondrial morphology assessment.<p> Sequencing of the particular regions of the Miniature Schnauzer Tfam gene revealed no significant nucleotide changes between affected and normal dogs. Evaluation of lymphocyte mitochondrial size, number and morphology also revealed no significant differences between the two groups. In the English Springer Spaniel dog a relative decrease in leukocyte mtDNA did not exist in dogs affected with retinal dysplasia. Furthermore, evaluation of affected English Springer Spaniel dog lymphocyte mitochondria revealed no significant differences in mitochondrial number, surface area or morphology when compared to normal English Springer Spaniel dogs.<p> To conclude, we failed to demonstrate a mutation in the areas of the Tfam gene sequenced in Miniature Schnauzers affected with retinal dysplasia and associated persistent hyperplastic primary vitreous. In contrast to previous findings of decreased leukocyte mtDNA in the affected Miniature Schnauzer dog, no evidence was found to support a relative decrease in leukocyte mtDNA in English Springer Spaniel dogs affected with retinal dysplasia. Furthermore, the hypothesis of altered mitochondrial size, number and morphology in affected dogs is not supported by this study. Further evaluation of mitochondria, mtDNA and mitochondrial gene expression within age-matched retina and RPE of Miniature Schnauzer and English Springer Spaniel dogs is necessary to determine if mitochondria and altered energy supply play a role in the pathogenesis of retinal dysplasia in these breeds.

The intent of this research is to identify a simple diagnostic test to detect abnormal calciuresis and predict calcium oxalate (CaOx) urolith presence in Miniature Schnauzers. We investigated the impact of postprandial time on the specificity of urine calcium:creatine (UCa/Cr) in identifying affected dogs. The hypotheses were: 1) Significant differences exist in fasted and postprandial UCa/Cr between urolith-forming and control schnauzers. 2) UCa/Cr increases significantly from fasted baseline at one or more postprandial time point(s). Urine samples were collected from Miniature Schnauzers with (urolith-formers) and without (controls) CaOx uroliths in a fasted state and 1, 2, 4, and 8 hours after feeding a standardized diet. The change in UCa/Cr from baseline was calculated for each postprandial time. Urolithiasis status and the time point were assessed for impact on the UCa/Cr and change in UCa/Cr using a mixed model ANOVA. Based on 9 urolith-forming and 15 control dogs enrolled, urolith-forming Miniature Schnauzers have significantly higher mean UCa/Cr at 1 hour and 8 hours postprandial timepoints indicating altered calciuresis. The change in UCa/Cr was not significant at any post-prandial time point between or within groups. This pilot study shows male urolith-forming Miniature Schnauzers have excessive calciuresis throughout the day, providing insight into the mechanism behind their formation of CaOx uroliths. If using the Ca/Cr ratio, the postprandial sampling time is not critical. This simple urine measurement has potential as a marker of urolith presence and possibly risk of urolith formation. / Master of Science

The relationship between hyperlipidemia and pancreatitis remains obscure in dogs. The aim of the present study was to investigate any possible association between hyperlipidemia and pancreatitis in dogs. In the first part of the study, Miniature Schnauzers with hypertriglyceridemia were found to have significantly higher serum cPLI concentrations than Miniature Schnauzers with normal serum triglyceride concentrations (P=0.0001). Also, Miniature Schnauzers with severe hypertriglyceridemia (>862 mg/dL) had 4.5 times higher odds (P=0.0343) for having a serum cPLI concentration consistent with pancreatitis. In the second part of the study, 17 Miniature Schnauzers prospectively enrolled with a history of pancreatitis were significantly more likely to have hypertriglyceridemia (71 percent) after resolution of pancreatitis than 34 age-matched Miniature Schnauzers without a history of pancreatitis (33 percent; odds ratio=5.02; P=0.0163). For the third part of the study, assessment of the feasibility and usefulness of a novel density gradient ultracentrifugation method using NaBiEDTA for lipoprotein profiling in dogs was attempted. Density gradient ultracentrifugation using NaBiEDTA was found to be useful for the study of lipoprotein profiles in dogs. Significant differences were detected in the lipoprotein profiles (mainly involving TRL and specific LDL fractions) among healthy Miniature Schnauzers, dogs of various other breeds, and hypertriglyceridemic Miniature Schnauzers. In the fourth part of the study, the effect of a commercially available low-fat diet on serum lipid and pancreas-specific lipase (Spec cPL) concentrations and lipoprotein profiles in Miniature Schnauzers with primary hypertriglyceridemia was evaluated. The study diet was found to be effective in significantly reducing serum triglyceride and cholesterol concentrations and changing the lipoprotein profiles of the dogs studied within 2 months. However, there was no significant effect of the study diet on serum Spec cPL concentrations. In the last part of the study, serum triglyceride and cholesterol concentrations and lipoprotein profiles were compared between dogs with naturally occurring pancreatitis and healthy dogs. The majority of dogs with naturally occurring pancreatitis had normal serum triglyceride and cholesterol concentrations. Important differences were identified in lipoprotein profiles between dogs with pancreatitis (higher LDL2, LDL3, and LDL4 fractions and lower TRL, HDL2a, and HDL3c fractions) and healthy control dogs.