MRI ischemic and hemorrhagic lesions in arterial and venous territories characterize central nervous system intravascular lymphoma in dogs.

Intravascular lymphoma (IVL) is characterized by the proliferation of large malignant lymphocytes within the lumen of blood vessels. This retrospective, multi-center, case series study aimed to describe the MRI features of confirmed central nervous system IVL in dogs and compare them with histopathological findings. Medical record databases from seven veterinary centers were searched for cases of histologically confirmed IVL. Dogs were included if an MRI was performed. The MRI studies and histopathology samples were reviewed to compare the MRI changes with the histopathological findings. Twelve dogs met the inclusion criteria (12 brains and three spinal cords). Imaging of the brains revealed multifocal T2-weighted/FLAIR hyperintense and T1-weighted iso-hypointense lesions, with variable contrast enhancement; areas of abnormal diffusion both in arterial and venous territories in diffusion-weighted imaging; and meningeal enhancement. On gradient echo images (GRE), the changes comprised tubular susceptibility artifacts, consistent with the "susceptibility vessel sign", and additional variably sized/shaped intraparenchymal susceptibility artifacts. Spinal cord lesions presented as fusiform T2-weighted hyperintensities with scattered susceptibility artifacts on GRE and variable parenchymal and meningeal contrast enhancement. On histopathology, subarachnoid hemorrhages and neuroparenchymal areas of edema and necrosis, with or without hemorrhage, indicating ischemic and hemorrhagic infarctions, were found. These lesions were concurrent with severely dilated meningeal and parenchymal arteries and veins plugged by neoplastic lymphocytes and fibrin. Due to the unique angiocentric distribution of IVL, ischemic and hemorrhagic infarcts of variable chronicity affecting both the arterial and venous territories associated with thrombi formation can be detected on MRI.

Preputial Demodex species in big brown bats (Eptesicus fuscus) in eastern Tennessee.

The presence of preputial Demodex species in four captive, wild-caught big brown bats (Eptesicus fuscus) in eastern Tennessee, USA, examined between 2008 and 2010 is reported. In three of four cases, there was associated folliculitis, dermatitis, or preputial adenitis. There were no clinical signs directly attributable to the mites, although penile prolapse was present in one case. Mites were retrieved from preputial skin samples of other archival big brown bats by potassium hydroxide digestion and analyzed by polymerase chain reaction (PCR). DNA sequencing of the 16S rRNA gene revealed 99.6% homology to Demodex canis, although morphologic differences distinguish the two species. Mites of this report differ in anatomic location from Demodex spp. previously reported in bats and represent a species unreported to public databases.

Suspected Macrorhabdosis during a Concurrent Salmonellosis Outbreak in a Wild Yellow-Rumped Warbler (Setophaga coronata).

We describe necropsy lesions of three adult Yellow-rumped Warblers (Setophaga coronata) diagnosed with salmonellosis during a Salmonella enterica serovar Typhimurium outbreak. One warbler had filamentous organisms consistent with Macrorhabdus ornithogaster at the proventricular-ventricular isthmus. There is limited information on Macrorhabdus ornithogaster infections in wild North American birds.

Detection of human papillomavirus DNA in feline premalignant and invasive squamous cell carcinoma.

Squamous cell carcinoma (SCC) is the most common malignant cutaneous and oral neoplasm of cats. Papillomavirus (PV) DNA has been identified in a proportion of feline Bowenoid in situ carcinomas (BISCs), cutaneous SCCs and a single oral SCC, but its exact role in the pathogenesis remains unknown. In humans, it has been suggested that ultraviolet (UV) light and human PV (HPV) may act as cofactors in cutaneous SCC carcinogenesis. Little is known about the influence of UV light on PV prevalence in feline cutaneous lesions, including actinic keratosis (AK). Additionally, PV prevalence in noncutaneous feline lesions, including oral SCC, is largely not known. This study aimed to determine the presence of PV in 84 cats with premalignant and invasive SCC from cutaneous and noncutaneous sites using polymerase chain reaction and to investigate an association with UV light. Papillomaviral DNA was amplified from two of 12 cases of AK, seven of 22 BISCs, nine of 39 cutaneous SCCs and two of 35 non-cutaneous SCCs. Of the PV DNA sequenced, 50% was most similar to HPV of the genus Betapapillomavirus, while the other 50% was most similar to Felis domesticus PV type 2. Exposure to UV was not associated with an increase in PV for cutaneous SCC. The results of this study suggest that in the cat, HPV DNA may be detectible within a higher percentage of squamous lesions than previously demonstrated, UV exposure may not be a confounder for PV presence, and noncutaneous lesions may have a low prevalence of PV.

Thyroid neoplasia in captive raccoons (Procyon lotor).

Two adult, spayed, female raccoons were diagnosed with thyroid neoplasia. One raccoon had a palpable, left-sided, nonfunctional thyroid adenocarcinoma which was treated with a thyroidectomy twice with local recurrence both times. After the second recurrence, pulmonary metastases were identified. A third thyroidectomy was performed, and a vascular access port was placed for administration of intravenous doxorubicin. The raccoon developed pancytopenia and became anorexic after chemotherapy, and the owner elected humane euthanasia. The second raccoon had nonpalpable, bilateral, functional follicular thyroid adenomatous hyperplasia and was treated with a right thyroidectomy and a partial left thyroidectomy, leaving behind the grossly normal portion of the left thyroid. However, the animal was still hyperthyroid after surgery and was then successfully managed with topical methimazole gel. Thyroid pathology has been documented in raccoons in Europe, but is not reported in the United States. Thyroid neoplasia in raccoons can occur as a nonfunctional adenocarcinoma, as is commonly reported in dogs, or as a functional adenoma, as is commonly reported in cats. Raccoons with adenocarcinomas should be evaluated for pulmonary metastasis. Methimazole gel may be a viable treatment option for raccoons with hyperthyroidism.

Immunohistochemical analysis of ocular hemangiomas and hemangiosarcomas in dogs.

PURPOSE: To determine if molecular markers typically associated with ultraviolet exposure could be detected in canine ocular hemangiomas (HA) and hemangiosarcomas (HSA). METHODS: Paraffin-embedded samples of canine ocular HA (n = 6) and HSA (n = 6) were examined for the presence of p53, p21, p16, cyclin D, PCNA, pAkt, telomerase, and estrogen receptor (ER)-alpha using immunohistochemistry. RESULTS: p53 and cyclin D protein were not detected in any of the canine HA or HSA samples. The majority of the HA and HSA were negative for both p21 and telomerase. pAkt immunoreactivity was absent in one HA, one HSA, but was present in five HA and five HSA. All of the HA or HSA samples were strongly positive for p16 and PCNA. ERalpha was expressed in all of the samples examined; there was more intense staining in the HSA samples compared to the HA samples. CONCLUSIONS: Results from this study describe the protein expression, via immunohistochemistry, that might be altered in UV exposure in HA and HAS formation. p53 may not play an important role in tumor development; rather, in the tumors examined, expression of cell cycle regulators independent of the p53 pathway appear central in HA and HSA formation and progression. In addition, this study finds that ERalpha may be involved in promoting the invasive behavior associated with HSA.

The acute cutaneous inflammatory response is attenuated in Slug-knockout mice.

We previously reported ultraviolet radiation (UVR) induction of Slug, a Snail family zinc-finger transcription factor, in the epidermis of mice; we now report that Slug-knockout mice are, unexpectedly, more resistant to sunburn than wild-type mice. There was a marked difference between the cutaneous inflammatory response in the skin of Slug-knockout and wild-type mice from 12 h to 1 week following a single exposure to 3 minimal erythemal doses of UVR. Slug-knockout mice showed a much reduced immediate increase in skin thickness and neutrophil infiltration compared to wild-type mice. However, there were as many or more intraepidermal T cells, dermal mast cells, and dermal blood vessels in the UVR-exposed skin of Slug-knockout mice as in the skin of wild-type mice. Differences in cytokine and chemokine expression following UVR appeared to account for at least some differences between the genotypes in cutaneous inflammatory response. Despite the reported antiapoptotic and antiproliferative role for Slug in some cell types, we observed little difference between the genotypes in UVR-induced keratinocyte apoptosis or proliferation. Our findings indicate an unexpected but important role for Slug in the acute cutaneous inflammatory response to UVR.

Repeated administration of tribromoethanol in C57BL/6NHsd mice.

We evaluated the effect of repeated intraperitoneal administration of tribromoethanol on various parameters in C57BL/6NHsd mice. Mice (n = 68) were randomly assigned to 1 of 7 groups to receive tribromoethanol (500 mg/kg IP) on day 0 or days 0 and 8; vehicle (tert-amyl alcohol in sterile water) only on day 0 or days 0 and 8; sterile water injection on day 0 or days 0 and 8; or no treatment. A single dose of tribromoethanol failed to produce loss of pedal reflex and had no effect on median food and water consumption but altered median body weight on days 1 through 4 when compared with that in mice that received vehicle only or no treatment. Median body weight did not differ between mice that received a single dose of tribromoethanol and those that received an injection of water. Among mice given 2 doses of tribromoethanol, induction time, anesthetic duration, and recovery time varied widely. Repeated administration of tribromoethanol had no effect on median food and water consumption or body weight compared with those in controls. Median liver weight was significantly greater in mice that received 2 doses compared with a single dose of tribromoethanol. Median liver weight did not differ between untreated mice and those that received tribromoethanol. No significant organ or tissue pathology was observed in any study animal. Although tribromoethanol did not produce morbidity, mortality, or pathologic changes in treated animals, we urge caution in use of tribromoethanol in C57BL/6NHsd mice due to its variable anesthetic effectiveness.

Slug/Snai2 is a downstream mediator of epidermal growth factor receptor-stimulated reepithelialization.

Many peptide growth factors, including EGFR ligands, accelerate wound reepithelialization in vivo and in vitro. Furthermore, EGFR expression is transiently increased at wound margins, suggesting an active role for this receptor in wound repair. During reepithelialization of cutaneous wounds, keratinocytes display a phenotypic plasticity resembling aspects of epithelial-mesenchymal transformation. The transcription factor Slug/Snai2 is a regulator of epithelial-mesenchymal transformation during development, and we previously reported that Slug expression is elevated in keratinocytes bordering cutaneous wounds in vivo, ex vivo, and in vitro. In this study we provide evidence that Slug expression is necessary for an EGFR-stimulated reepithelialization response. Epidermal growth factor (EGF) induces Slug expression and the response to EGFR activation is more robust than to other receptor tyrosine kinase ligands. EGFR-stimulated reepithelialization is highly dependent on Slug, as demonstrated by the absence of EGF-stimulated outgrowth in explants derived from Slug null mice. In vitro reepithelialization stimulated by ectopic Slug expression was not impaired by an inhibitor of EGFR catalytic activity, suggesting that Slug is a downstream mediator of this EGFR-stimulated response. Our findings provide evidence that Slug is an essential component of the pathway leading to EGFR-mediated epithelial outgrowth.

Cutaneous wound reepithelialization is compromised in mice lacking functional Slug (Snai2).

BACKGROUND: Keratinocytes at wound margins undergo partial epithelial to mesenchymal transition (EMT). Based on previous in vitro and ex vivo findings, Slug (Snai2), a transcriptional regulator of EMT in development, may play an important role in this process. OBJECTIVES: This study was designed to validate an in vivo role for Slug in wound healing. METHODS: Excisional wounds in Slug null and wild type mice were examined histologically at 6, 24, 48, and 72h after wounding; reepithelialization was measured and immunohistochemistry for keratins 8, 10, 14, and 6 and E-cadherin was performed. In 20 Slug null and 20 wild type mice exposed three times weekly to two minimal erythemal doses of UVR, the development of non-healing cutaneous ulcers was documented. Ulcers were examined histologically and by immunohistochemistry. RESULTS: The reepithelialization component of excisional wound healing was reduced 1.7-fold and expression of the Slug target genes keratin 8 and E-cadherin was increased at wound margins in Slug null compared to wild type mice. In contrast, no differences in expression of keratins 10 or 14 or in markers of proliferation K6 and Ki-67 were observed. Forty per cent of Slug null mice but no wild type mice developed non-healing cutaneous ulcers in response to chronic UVR. Keratinocytes at ulcer margins expressed high levels of keratin 8 and retained E-cadherin expression, thus resembling excisional wounds. CONCLUSION: Slug is an important modulator of successful wound repair in adult tissue and may be critical for maintaining epidermal integrity in response to chronic injury.

Microarray analysis demonstrates a role for Slug in epidermal homeostasis.

Slug (Snail2) is a member of the Snail family of zinc-finger transcription factors with regulatory functions in development, tissue morphogenesis, and tumor progression. Little is known about Slug in normal adult tissue; however, a role for Slug in the skin was suggested by our previous observations of Slug expression in normal murine keratinocytes and Slug induction at wound margins. To study the impact of Slug in the skin, we compared patterns of gene expression in epidermis from Slug-null and wild-type mice. A total of 139 genes had significantly increased, and 109 genes had significantly decreased expression in Slug knockout epidermis. Altered expression of selected genes in Slug knockout epidermis was validated by real-time PCR and immunohistochemistry. Previously reported Slug targets were identified, in addition to novel genes, including cytokeratins, adhesion molecules, and extracellular matrix components. Functional classification of altered gene expression was consistent with a role for Slug in keratinocyte development and differentiation, proliferation, apoptosis, adhesion, motility, as well as angiogenesis and response to environmental stimuli. These results highlight the utility of genetic models to study the in vivo impact of regulatory factors in unperturbed skin and suggest that Slug has significant activities in the adult epidermis.

Snai2 expression enhances ultraviolet radiation-induced skin carcinogenesis.

Snai2, encoded by the SNAI2 gene, has been shown to modulate epithelial-mesenchymal transformation (EMT), the conversion of sessile epithelial cells attached to adjacent cells and to the basement membrane into dissociated and motile fibroblastic cells. EMT occurs during development, wound healing, and carcinoma progression. Using Snai2-null mice (Snai2(lacZ)), we evaluated the role of Snai2 in UV radiation (UVR)-induced skin carcinogenesis. In chronically UVR-exposed nontumor-bearing skin from Snai2-null mice, inflammation and epidermal proliferation were decreased compared with wild-type (+/+) skin. Snai2-null mice had a consistently lower tumor burden than +/+ mice. In addition, null mice developed fewer aggressive spindle cell tumors, believed to arise from squamous cell carcinomas that have undergone EMT, than +/+ mice; however, the difference in tumor type distribution between the two genotypes was not statistically significant. No metastases were observed in either the +/+ or Snai2-null mice. Using quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry, we showed that the spindle cell tumors in the Snai2-null mice demonstrated impaired EMT, as shown by decreased vimentin and increased cadherin 1 expression. This study confirms a role for Snai2 in EMT, but demonstrates that Snai2 expression is not required for the development or progression of UVR-induced skin tumors.

Ultraviolet radiation-induced corneal degeneration in 129 mice.

Ultraviolet radiation (UVR) is a risk factor for the development of ocular disease in humans, including acute photokeratitis, chronic corneal spheroidal degeneration, and cataract formation. This report describes the ocular lesions seen in 21 mice chronically exposed to UVR as part of a skin carcinogenicity study. All globes were affected to varying degrees. The primary lesion, not previously reported in UVR-exposed mice, was marked loss of keratocytes relative to age-matched controls. Secondary lesions included corneal stromal thinning, keratoconus, corneal vascularization and fibrosis, keratitis, globe rupture, and phthisis bulbi. In addition, more than 90% of UVR-exposed and unexposed lenses had evidence of cataract formation; this is the first report of the occurrence of spontaneous cataracts in 129 mice. In a subsequent study, apoptotic cells were identified histologically and by cleaved caspase 3 immunoreactivity in the corneal epithelium and, less commonly, in the corneal stroma after acute UVR exposure. Based on this finding, we propose that the loss of keratocytes observed in the chronic study was due to UVR-induced apoptosis.

Ultraviolet radiation stimulates expression of Snail family transcription factors in keratinocytes.

The related zinc finger transcription factors Slug and Snail modulate epithelial mesenchymal transformation (EMT), the conversion of sessile epithelial cells into migratory fibroblast-like cells. EMT occurs during development, wound healing, and tumor progression. Growth factors, acting through mitogen-activated protein kinase (MAPK) cascades, regulate expression of Slug and Snail. Expression of Snail family transcription factors appears to be elevated in UVR-induced murine squamous cell carcinomas (SCC). We report here that ultraviolet radiation (UVR), which activates MAPK cascades, also stimulates Snail and Slug expression in epidermal keratinocytes. UVR exposure transiently elevated Slug and Snail mRNA expression in human keratinocytes in vitro and mouse epidermis in vivo. This induction was mediated, at least in part, through the ERK and p38 MAPK cascades, as pharmacological inhibition of these cascades partially or completely blocked Slug and Snail induction by UVR. On the other hand, UVR induction of Slug and Snail was enhanced by inhibition of JNK. Slug appears to play a functional role in the acute response of keratinocytes to UVR, as UVR induction of keratin 6 in the epidermis of Slug knockout mice was markedly delayed compared to wild-type mice. Slug and Snail are known to regulate molecules important in the cytoskeleton, intercellular adhesion, cell motility, and apoptosis, thus it seems probable that transiently or persistently elevated expression of these factors fosters the progression of UVR-induced SCC.