Biomechanical evaluation of the stabilizing function of the atlantoaxial ligaments under shear loading: A canine cadaveric study

OBJECTIVES To evaluate the stabilizing function of atlanto-axial ligaments in dogs. STUDY DESIGN Cadaveric biomechanical study. ANIMALS Beagle dog cadavers (n = 10). METHODS The craniocervical region was collected from 10 Beagle cadavers, and the occipito-atlanto-axial region was prepared and freed from the surrounding muscles. Care was taken to preserve integrity of the atlantoaxial ligaments and atlantoaxial joint capsule. The atlanto-occipital joints were blocked with 2 diverging transarticular 1.8 mm positive threaded K-wires. Specimen extremities were embedded in polymethylmethacrylate (PMMA) and mounted on a simulator testing shear load at the atlantoaxial joint. Range of motion (ROM) and neutral zone (NZ) were determined with all ligaments intact, after cutting the apical ligament, both alar ligaments, the transverse ligaments and finally after cutting the dorsal atlantoaxial ligament. RESULTS ROM increased similarly and stepwise during testing. The most significant increase was observed after transection of the alar ligaments. CONCLUSION The alar ligaments seem to be the most important ligamentous structures for stabilization of the atlantoaxial joint under shear load.

Canine noninflammatory alopecia: a comprehensive evaluation of common and distinguishing histological characteristics

BACKGROUND Noninflammatory alopecia is a frequent problem in dogs, and the pathogenesis is still unclear. OBJECTIVE The objective of this study was a comparative histological description of skin biopsies from dogs with different alopecic disorders and control dogs matched for coat type, season and disease duration. ANIMALS Twenty-one cases of alopecia X in plush-coated dogs, 12 cases of recurrent flank alopecia, three cases of hyperestrogenism, 15 cases of hyperadrenocorticism, 12 cases of hypothyroidism and 12 cases of primary alopecic disorders of unknown cause were evaluated. The controls were biopsies from 38 dogs of different coat types. METHODS We evaluated five serial sections of each biopsy histologically and immunohistologically to compare the histological findings within the disease groups and with the control. RESULTS All the dogs with hair cycle disorders had a significant increase in the number of hairless hair follicles, which we assigned to kenogen. In addition, dogs with alopecia X had the lowest percentage of anagen follicles and the highest percentage of telogen follicles. CONCLUSIONS The marked increase in kenogen follicles is a strong indication that the induction of the new anagen phase is impaired in hair cycle disorders. The findings in dogs with alopecia X further suggest that premature catagen is also involved in the pathogenesis. Further work to investigate the stem cell compartment and possible initiating factors for the different cycle phases is required to elucidate the exact pathogenesis.

Lateral incisor agenesis, canine impaction and characteristics of supernumerary teeth in a South European male population

Objective: To assess the prevalence of lateral incisor agenesis impacted canines and supernumerary teeth in a young adult male population. Materials and Methods: The panoramic radiographs of 1745 military students (mean age: 18.6 ± 0.52 years) who attended the Center of Aviation Medicine of the Armed Forces of Greece during the period 1997-2011 were initially analyzed for lateral incisor agenesis by two observers. After exclusion of the known orthodontic cases, a subgroup of 1636 examinees (mean age: 18.6 ± 0.44 years) was evaluated for canine impaction and supernumerary teeth. Results: Twenty-eight missing lateral incisors were observed in 22 military students, indicating an incidence of 1.3% in the investigated population. No lateral incisor agenesis was detected in the mandibular arch. A prevalence rate of 0.8% was determined for canine impaction in the sample of young adults. The majority of impacted teeth (86.7%) were diagnosed in the maxillary arch. Thirty-five supernumerary teeth were observed in 24 examinees (prevalence rate: 1.5%). The ratio of supernumerary teeth located in the maxilla versus the mandible was 2.2:1. The most common type of supernumerary tooth was the upper distomolar. Conclusion: The prevalence of lateral incisor agenesis, canine impaction, and supernumerary teeth ranged from 0.8 to 1.5% in the sample of male Greek military students.

Expression of thymic stromal lymphopoietin in canine atopic dermatitis

BACKGROUND In humans, thymic stromal lymphopoietin (TSLP) plays a central role in the development of allergic inflammation, such as atopic dermatitis (AD), but it is unknown whether it is involved in the pathogenesis of canine AD (CAD). HYPOTHESIS/OBJECTIVES Our aim was to characterize canine TSLP and to assess its expression in CAD. METHODS Canine TSLP was identified based on sequence homology with human TSLP and the complementary DNA (cDNA) cloned by RT-PCR. Real-time quantitative RT-PCR was established to assess the expression of canine TSLP in cultured canine keratinocytes and in skin biopsy specimens from lesional and nonlesional skin of 12 dogs with CAD and eight healthy control dogs. RESULTS Partial canine TSLP cDNA was cloned and characterized. It contained four exons that shared 70 and 73% nucleotide identity with human and equine TSLP, respectively, encoding the signal peptide and full-length secreted protein. We found significantly increased TSLP expression in lesional and nonlesional skin of dogs with CAD compared with healthy control dogs (P < 0.05), whereas no difference was measured between lesional and nonlesional samples. In cultured primary canine keratinocytes, we found increased TSLP expression after stimulation with house dust mite allergen extract or Toll-like receptor ligands lipopolysaccharide and poly I:C. CONCLUSIONS AND CLINICAL IMPORTANCE Increased TSLP expression in the skin of dogs with CAD supports an involvement of TSLP in the pathogenesis of CAD similar to that in humans. Further studies should elucidate the function and therapeutic potential of TSLP in CAD.

Immunohistochemical evaluation of heat shock protein expression in normal canine nerve and peripheral nerve sheath tumours

Abnormal expression of heat shock proteins (HSPs) has been observed in many human neoplasms and such expression has prognostic, predictive and therapeutic implications. The aim of this study was to evaluate immunohistochemically the expression of HSP 27, HSP 32 and HSP 90 in normal canine peripheral nerves and in four benign and 15 malignant canine peripheral nerve sheath tumours (PNSTs). In normal nerve, all of the HSPs were detected in axons, epineurial fibroblasts and scattered Schwann cell bodies. Cytoplasmic expression of HSP 27 was more widespread and intense in benign PNSTs compared with malignant PNSTs (P <0.05). Widespread and intense nuclear expression of HSP 32 was also associated with benign tumours (P <0.01), while high HSP 90 immunoreactivity was detected in all tumours, suggesting that HSP 90 might represent a new therapeutic target.

[Concurrent irradiation and DNA tumor vaccination in canine oral malignant melanoma: a pilot study].

Melanoma is the most common oral tumor in dogs, characterized by rapid growth, local invasion, and high metastatic rate. The goal of this study was to evaluate the combination of radiation therapy and DNA tumor vaccine. We hypothesized, that the concurrent use would not increase toxicity. Nine dogs with oral melanoma were treated with 4 fractions of 8 Gray at 7-day intervals. The vaccine was given 4 times every 14 days, beginning at the first radiation fraction. Local acute radiation toxicities were assessed according to the VRTOG toxicity scoring scheme over a time period of 7 weeks. In none of the evaluated dogs, mucositis, dermatitis and conjunctivitis exceeded grade 2. In 3 dogs mild fever, lethargy, and local swelling at the injection site were seen after vaccine application. In conclusion, the concurrent administration of radiation therapy and vaccine was well tolerated in all dogs.

Canine keratinocytes upregulate type I interferons and proinflammatory cytokines in response to poly(dA:dT) but not to canine papillomavirus.

Papillomaviruses (PV) are double stranded (ds) DNA viruses that infect epithelial cells within the skin or mucosa, most often causing benign neoplasms that spontaneously regress. The immune system plays a key role in the defense against PVs. Since these viruses infect keratinocytes, we wanted to investigate the role of the keratinocyte in initiating an immune response to canine papillomavirus-2 (CPV-2) in the dog. Keratinocytes express a variety of pattern recognition receptors (PRR) to distinguish different cutaneous pathogens and initiate an immune response. We examined the mRNA expression patterns for several recently described cytosolic nucleic acid sensing PRRs in canine monolayer keratinocyte cultures using quantitative reverse transcription-polymerase chain reaction. Unstimulated normal cells were found to express mRNA for melanoma differentiation associated gene 5 (MDA5), retinoic acid-inducible gene I (RIG-I), DNA-dependent activation of interferon regulatory factors, leucine rich repeat flightless interacting protein 1, and interferon inducible gene 16 (IFI16), as well as their adaptor molecules myeloid differentiation primary response gene 88, interferon-β promoter stimulator 1, and endoplasmic reticulum-resident transmembrane protein stimulator of interferon genes. When stimulated with synthetic dsDNA [poly(dA:dT)] or dsRNA [poly(I:C)], keratinocytes responded with increased mRNA expression levels for interleukin-6, tumor necrosis factor-α, interferon-β, RIG-I, IFI16, and MDA5. There was no detectable increase in mRNA expression, however, in keratinocytes infected with CPV-2. Furthermore, CPV-2-infected keratinocytes stimulated with poly(dA:dT) and poly(I:C) showed similar mRNA expression levels for these gene products when compared with expression levels in uninfected cells. These results suggest that although canine keratinocytes contain functional PRRs that can recognize and respond to dsDNA and dsRNA ligands, they do not appear to recognize or initiate a similar response to CPV-2.

Antimicrobial susceptibility of canine Clostridium perfringens strains from Switzerland

Fifty Clostridium perfringens strains were isolated from individual dogs with acute diarrhoea that were not given antibiotics. Toxin types and minimal inhibitory concentrations of 15 antibiotics were determined for each of them. All strains harboured the alpha-toxin gene, 12 of them had both the alpha- and entero-toxin gene and 5 had both the alpha- and beta2-toxin gene. Eighteen percent of the isolates showed resistance to tetracycline and 54 % showed decreased susceptibility to metronidazole which is one of the most frequently used antibiotics in the treatment of canine diarrhoea. Apart from that, all isolates were susceptible to the remaining antibiotics tested. These findings lead to the conclusion that despite a general susceptibility to antibiotics in C. perfringens, resistance is developing in isolates from dogs. Therefore, careful identification of the pathogenic agent and antibiotic susceptibility testing should be performed prior to therapy in order to minimise further selection of antibiotic resistance.

Validation of stress magnetic resonance imaging of the canine stifle joint with and without an intact cranial cruciate ligament.

OBJECTIVE To validate use of stress MRI for evaluation of stifle joints of dogs with an intact or deficient cranial cruciate ligament (CrCL). SAMPLE 10 cadaveric stifle joints from 10 dogs. PROCEDURES A custom-made limb-holding device and a pulley system linked to a paw plate were used to apply axial compression across the stifle joint and induce cranial tibial translation with the joint in various degrees of flexion. By use of sagittal proton density-weighted MRI, CrCL-intact and deficient stifle joints were evaluated under conditions of loading stress simulating the tibial compression test or the cranial drawer test. Medial and lateral femorotibial subluxation following CrCL transection measured under a simulated tibial compression test and a cranial drawer test were compared. RESULTS By use of tibial compression test MRI, the mean ± SD cranial tibial translations in the medial and lateral compartments were 9.6 ± 3.7 mm and 10 ± 4.1 mm, respectively. By use of cranial drawer test MRI, the mean ± SD cranial tibial translations in the medial and lateral compartments were 8.3 ± 3.3 mm and 9.5 ± 3.5 mm, respectively. No significant difference in femorotibial subluxation was found between stress MRI techniques. Femorotibial subluxation elicited by use of the cranial drawer test was greater in the lateral than in the medial compartment. CONCLUSIONS AND CLINICAL RELEVANCE Both stress techniques induced stifle joint subluxation following CrCL transection that was measurable by use of MRI, suggesting that both methods may be further evaluated for clinical use.