Objective—To investigate whether circulating concentrations of biomarkers of glucose homeostasis, progesterone, and growth hormone in healthy female Elkhounds differ during diestrus and anestrus and to compare those findings with data from dogs of other breeds.
Animals—22 healthy female dogs of Elkhound breeds (known to have a high incidence of diestrus-associated diabetes mellitus) and 18 healthy female non-Elkhound dogs.
Procedures—For each dog, a blood sample (12 mL) was collected once during anestrus and once 2 to 8 weeks after cessation of estrual bleeding. Serum or whole blood samples were analyzed for glucose, growth hormone, insulin-like growth factor-1, C-peptide, fructosamine, and glycated hemoglobin A1c concentrations. Homeostasis model assessments (HOMAs) of pancreatic beta-cell function and insulin secretion were calculated.
Results—In Elkhounds, C-peptide concentration and the HOMA for beta-cell function (markers of insulin secretion) were higher in samples obtained during diestrus, compared with findings in samples obtained during anestrus. The HOMA for insulin sensitivity was lower (albeit not significantly) during diestrus than it was during anestrus in Elkhounds. Markers of insulin secretion and sensitivity were similar during anestrus and diestrus in the dogs of other breeds. Serum progesterone concentrations were greater during diestrus than during anestrus in Elkhounds and non-Elkhound dogs. All other variables did not differ between diestrus and anestrus within or between the 2 breed groupings.
Conclusions and Clinical Relevance—Results provided evidence that circulating insulin concentrations during diestrus are higher than those during anestrus in Elkhounds, which could contribute to development of diestrus-associated diabetes mellitus.
Objective—To develop a reverse transcriptase-polymerase
chain reaction (RT-PCR) assay to detect
canine melanoma-associated antigens (MAAs) and to
use this technique to screen aspirates of lymph
nodes (LNs) for evidence of metastatic spread of oral
Animals—7 dogs with oral malignant melanoma and
4 dogs with multicentric lymphosarcoma.
Procedures—We prepared cDNA from melanoma
tumor biopsies and fine-needle aspirates obtained
from submandibular LNs of dogs with oral malignant
melanoma or multicentric lymphosarcoma. The RTPCR
assay was performed by use of tyrosinase,
Melan-A, gp100, tyrosinase-related protein 2 (TRP-2),
or melanoma antigen-encoding gene B (MAGE-B)-
Results—We detected MAGE-B mRNA in canine testicular
tissue but not in melanoma biopsy specimens.
Tyrosinase, Melan-A, gp100, and TRP-2 mRNAs were
detected in tumor biopsy specimens and in 2 of 5 LN
aspirates from dogs with melanoma, suggesting
metastatic spread in those 2 dogs. We did not detect
MAAs in LN aspirates obtained from dogs with multicentric
lymphosarcoma. Sequencing of canine Melan-
A and gp100 PCR products confirmed the specificity
of the assay for these genes.
Conclusions and Clinical Relevance—Clinical staging
of dogs with oral malignant melanoma is useful to
assist in designing appropriate treatments. However,
results of histologic examination of LN biopsy specimens
can be inconclusive and, in humans, can underestimate
the number of patients with metastatic disease.
Molecular staging of melanomas in dogs can be
achieved by screening LN aspirates for MAA mRNA,
and this can be performed in combination with cytologic
examination to aid in detection of metastatic disease.
( Am J Vet Res 2003;64:544–549)
Objective—To characterize variability in melanoma-associated antigen (MAA) genes and gene expression in melanomas of dogs.
Animals—18 dogs with malignant melanomas and 8 healthy control dogs.
Procedures—cDNA was prepared from malignant melanoma biopsy specimens and from pigmented oral mucocutaneous tissues of healthy control dogs. Genomic DNA was extracted from poorly pigmented melanomas. A PCR assay was performed by use of Melan-A, SILV, or tyrosinase-specific primers.
Results—Splice variants of Melan-A and SILV were identified in malignant melanomas and also in healthy pigmented tissues, whereas a tyrosinase splice variant was detected in melanoma tissues only. A short interspersed nuclear element (SINE) insertion mutation was identified in the SILV gene in 1 of 10 poorly pigmented melanomas. Six novel exonic single nucleotide polymorphisms (SNPs; 3 synonymous and 3 nonsynonymous) were detected in the tyrosinase gene, and 1 nonsynonymous exonic SNP was detected in the SILV gene.
Conclusions and Clinical Relevance—Variants of MAA mRNA were detected in malignant melanoma tissues of dogs. The importance of MAA alternative transcripts expressed in melanomas and normal pigmented tissues was unclear, but they may have represented a means of regulating melanin synthesis. The tyrosinase splice variant was detected only in melanomas and could potentially be a tumor-specific target for immunotherapy. A SILV SINE insertion mutation was identified in a melanoma from a Great Dane, a breed known to carry this mutation (associated with merle coat color). The nonsynonymous SNPs detected in tyrosinase and SILV transcripts did not appear to affect tumor pigmentation.