Relative quantification of white blood cell mitochondrial DNA and assessment of mitochondria by use of transmission electron microscopy in English Springer Spaniels with and without retinal dysplasia

Bianca S. Bauer Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.

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George W. Forsyth Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.

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Lynne S. Sandmeyer Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.

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Bruce H. Grahn Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.

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Abstract

Objective—To compare relative amounts of WBC mitochondrial DNA (mtDNA; assessed via real-time PCR assay) and morphology of lymphocyte mitochondria (assessed via transmission electron microscopy [TEM]) in blood samples collected from English Springer Spaniels with and without retinal dysplasia.

Animals—7 and 5 client-owned English Springer Spaniels (1 to 11 years old) with and without retinal dysplasia, respectively.

Procedures—Blood samples were obtained from affected and unaffected dogs via venipuncture. Genomic DNA was extracted from WBCs of the 7 affected and 5 unaffected dogs, and relative quantification of the cytochrome c oxidase subunit 1 gene (COX1) was determined via analysis of real-time PCR results. White blood cells from 3 affected and 4 unaffected dogs were embedded in epoxide resin for TEM; cross sections were examined for lymphocytes, which were measured. The mitochondria within lymphocytes were quantified, and the mitochondrial surface area per lymphocyte cross section was calculated. A masked technique was used to compare mitochondrial morphology between the 2 groups.

Results—Compared with the smallest measured quantity of mtDNA among unaffected dogs, mtDNA amounts varied among unaffected (1.08- to 4.76-fold differences) and affected dogs (1- to 2.68-fold differences). Analysis of lymphocyte measurements and mitochondrial surface area, morphology, and quantity revealed no significant differences between affected and unaffected dogs.

Conclusions and Clinical Relevance—No significant differences were detected in relative amounts of WBC mtDNA or the size, number, or morphology of lymphocyte mitochondria in English Springer Spaniels affected with retinal dysplasia, compared with results for unaffected control dogs.

Abstract

Objective—To compare relative amounts of WBC mitochondrial DNA (mtDNA; assessed via real-time PCR assay) and morphology of lymphocyte mitochondria (assessed via transmission electron microscopy [TEM]) in blood samples collected from English Springer Spaniels with and without retinal dysplasia.

Animals—7 and 5 client-owned English Springer Spaniels (1 to 11 years old) with and without retinal dysplasia, respectively.

Procedures—Blood samples were obtained from affected and unaffected dogs via venipuncture. Genomic DNA was extracted from WBCs of the 7 affected and 5 unaffected dogs, and relative quantification of the cytochrome c oxidase subunit 1 gene (COX1) was determined via analysis of real-time PCR results. White blood cells from 3 affected and 4 unaffected dogs were embedded in epoxide resin for TEM; cross sections were examined for lymphocytes, which were measured. The mitochondria within lymphocytes were quantified, and the mitochondrial surface area per lymphocyte cross section was calculated. A masked technique was used to compare mitochondrial morphology between the 2 groups.

Results—Compared with the smallest measured quantity of mtDNA among unaffected dogs, mtDNA amounts varied among unaffected (1.08- to 4.76-fold differences) and affected dogs (1- to 2.68-fold differences). Analysis of lymphocyte measurements and mitochondrial surface area, morphology, and quantity revealed no significant differences between affected and unaffected dogs.

Conclusions and Clinical Relevance—No significant differences were detected in relative amounts of WBC mtDNA or the size, number, or morphology of lymphocyte mitochondria in English Springer Spaniels affected with retinal dysplasia, compared with results for unaffected control dogs.

Contributor Notes

Supported by the Companion Animal Health Fund (Western College of Veterinary Medicine).

Presented at the 39th Annual American College of Veterinary Ophthalmology Conference, Boston, October 2008.

Address correspondence to Dr. Bauer (bianca.bauer@usask.ca).
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