Dr. Teixeira is a Board Certified Veterinary Pathologist and an Assistant Professor at the School of Veterinary Medicine, University of Wisconsin-Madison. His clinical and research interests include comparative ocular pathology, microscopic imaging (light and electron microscopy, multiphoton laser-scanning microscopy and computational image analysis) and extracellular matrix alterations in ocular disease. Other research interests include animal models of glaucoma, ocular immunopathology and morphology of ocular neovascular diseases.
Collagen crosslinking impacts stromal wound healing and haze formation in a rabbit phototherapeutic keratectomy model
Mol Vis. 2023 Jul 16;29:102-116. eCollection 2023.
PURPOSE: The purpose of this study was to evaluate the elastic modulus, keratocyte-fibroblast-myocyte transformation, and haze formation of the corneal stroma following combined phototherapeutic keratectomy (PTK) and epithelium-off UV-A/riboflavin corneal collagen crosslinking (CXL) using an in vivo rabbit model.
METHODS: Rabbits underwent PTK and CXL, PTK only, or CXL 35 days before PTK. Rebound tonometry, Fourier-domain optical coherence tomography, and ultrasound pachymetry were performed on days 7, 14, 21, 42, 70, and 90 post-operatively. Atomic force microscopy, histologic inflammation, and immunohistochemistry for α-smooth muscle actin (α-SMA) were assessed post-mortem.
RESULTS: Stromal haze formation following simultaneous PTK and CXL was significantly greater than in corneas that received PTK only and persisted for more than 90 days. No significant difference in stromal haze was noted between groups receiving simultaneous CXL and PTK and those receiving CXL before PTK. Stromal inflammation did not differ between groups at any time point, although the intensity of α-SMA over the number of nuclei was significantly greater at day 21 between groups receiving simultaneous CXL and PTK and those receiving CXL before PTK. The elastic modulus was significantly greater in corneas receiving simultaneous CXL and PTK compared with those receiving PTK alone.
CONCLUSIONS: We showed that stromal haze formation and stromal stiffness is significantly increased following CXL, regardless of whether it is performed at or before the time of PTK. Further knowledge of the biophysical cues involved in determining corneal wound healing duration and outcomes will be important for understanding scarring following CXL and for the development of improved therapeutic options.
Iridial melanocytoma in a ferruginous hawk (Buteo regalis): A case report and review of avian melanocytic neoplasia
Vet Ophthalmol. 2023 Sep;26(5):464-471. doi: 10.1111/vop.13141. Epub 2023 Aug 15.
A 21-year-old, suspected female captive ferruginous hawk (Buteo regalis) was followed for 3 years due to an iridial mass of the left eye (OS) that progressively increased in size. Enucleation of OS was eventually recommended due to the iridial mass taking up approximately 75% of the anterior chamber, and the bird seemed less active. A complete physical examination, complete blood cell count, biochemistry, and survey radiographs were performed pre-surgery with no findings indicating metastasis. A subconjunctival enucleation was performed and the globe was submitted for histopathology through the Comparative Ocular Pathology Lab of Wisconsin. The histopathologic evaluation determined the mass to be consistent with an iris melanocytoma, which has not been previously reported in this species. The patient recovered well from surgery and has remained comfortable and active for 117 days post-surgery. This case report aimed to review the current available information on avian ocular neoplasms as well as describe the clinical presentation, medical management and surgical procedure, and long-term follow-up for this patient to enhance clinical understanding of the behavior of iris melanocytic tumors in avian species.
Clinical and histopathological features of proliferative corneal lesions in Cyprininae fishes: Implications for treatment and insights into corneal tumors
Vet Ophthalmol. 2023 Jul 23. doi: 10.1111/vop.13133. Online ahead of print.
Captive fish populations, such as those encompassing aquarium and pet fish, offer significant economic value and are integral to conservation, research, and education. However, these ornamental fish exhibit a reduced ability to protect their ocular surfaces, and our understanding of the ocular diseases that affect them remains limited. Although corneal neoplasms in carp are uncommon, identifying their distinct characteristics is crucial in selecting appropriate therapeutic interventions that aim to preserve vision, prevent the ocular loss, and ultimately ensure the survival of the affected fish. This study provides clinical and histopathological details of various proliferative corneal masses in Cyprininae species, including five koi (Cyprinus carpio) and four goldfish (Carassius auratus). It discusses a spectrum of neoplasms, including soft tissue sarcoma, spindle cell sarcoma, chromatophoroma, and papilloma, in addition to conditions like exuberant granulation tissue and proliferative carp pox. These findings bear significant implications for clinical decision-making and treatment, offering valuable insights into the incidence and characteristics of corneal tumors in captive fish, which could inform further studies in this area.
Atypical chorioretinal lesions in Siberian Husky dogs with primary angle-closure glaucoma: a case series
BMC Vet Res. 2022 May 16;18(1):182. doi: 10.1186/s12917-022-03259-8.
BACKGROUND: A number of etiologies for different canine chorioretinal lesions have been proved or suggested but some fundic lesions remain unclear in terms of an etiologic diagnosis, treatment options and prognosis. The purpose of this case series is to describe atypical chorioretinal lesions observed in dogs with primary angle-closure glaucoma (PACG).
CASE PRESENTATION: Two spayed-female Siberian Huskies (3- and 4-year-old) and one Siberian Husky/Australian Shepherd mixed breed dog (11-month-old) that had multifocal depigmented retinal lesions and PACG were included.
PROCEDURES: Ophthalmic examination, gross, and histopathologic examination findings are described. One of the dogs underwent further clinical diagnostics. Advanced clinical diagnostics on the fellow, presumed to be non-glaucomatous eye of a dog revealed: pectinate ligament dysplasia by gonioscopy, retinal thinning in the depigmented area and wedge shaped retinal thinning with delayed choroidal vascular perfusion by optical coherence tomography, confocal scanning laser ophthalmoscopy, fluorescein and indocyanine green angiography. Quantifiable maze testing for the same eye revealed mild nyctalopia but the full-field electroretinogram showed no generalized decrease of retinal function. Genetic testing for mutations within the retinitis pigmentosa GTPase regulator gene causing X-linked progressive retinal atrophy in Siberian Huskies was negative. Histopathologic evaluations on enucleated eyes in two dogs confirmed goniodysgenesis, PACG with optic nerve head cupping, and diffuse inner retinal atrophy. In addition, segmental profound retinal atrophy, loss of retinal pigment epithelium, and adhesion of the retina to Bruch's membrane was observed and coincided with multifocal depigmented lesions noted on fundic examination.
CONCLUSIONS: To our knowledge, this is the first case series with clinical and histopathologic data of chorioretinal lesions, most likely caused by severely impaired choroidal perfusion. Further studies are warranted to elucidate the etiology and pathophysiology, including its possible association with PACG.
Bifunctional Peptide that Anneals to Damaged Collagen and Clusters TGF-β Receptors Enhances Wound Healing
ACS Chem Biol. 2022 Feb 18;17(2):314-321. doi: 10.1021/acschembio.1c00745. Epub 2022 Jan 27.
Transforming growth factor-β (TGF-β) plays important roles in wound healing. The activity of TGF-β is initiated upon the binding of the growth factor to the extracellular domains of its receptors. We sought to facilitate the activation by clustering these extracellular domains. To do so, we used a known peptide that binds to TGF-β receptors without diminishing their affinity for TGF-β. We conjugated this peptide to a collagen-mimetic peptide that can anneal to the damaged collagen in a wound bed. We find that the conjugate enhances collagen deposition and wound closure in mice in a manner consistent with the clustering of TGF-β receptors. This strategy provides a means to upregulate the TGF-β signaling pathway without adding exogenous TGF-β and could inspire means to treat severe wounds.
Mapping retinal ganglion cell somas in a large-eyed glaucoma model
Mol Vis. 2021 Nov 19;27:608-621. eCollection 2021.
PURPOSE: The purpose of this study was to identify a robust, representative region of interest (ROI) for studies of retinal ganglion cell (RGC) soma loss in feline congenital glaucoma (FCG), a spontaneous, large-eyed glaucoma model.
METHODS: Seven FCG and three wild-type (wt) eyes were collected from 10 adult cats of both sexes. Eyes enucleated postmortem were immediately fixed overnight in 4% paraformaldehyde and then stored in 0.1 M PBS at 4 °C. The retinas were wholemounted, Nissl stained with cresyl violet, and imaged using light microscopy. Somas of RGCs were manually identified according to long-established morphological criteria and quantified using a semiautomated method; their coordinates were used to create density maps and plots of the retinal topography. The RGC axon counts for the corresponding eyes were obtained from glutaraldehyde-fixed, resin-embedded optic nerve cross-sections stained with 0.1% p-phenylenediamine (PPD) using a semiautomated counting method. Correlations between total optic nerve axons and RGC soma counts were assessed by linear regression. A k-means cluster algorithm was used to identify a retinal ROI, with further definition using a probability density algorithm.
RESULTS: Interindividual variability in RGC total soma counts was more pronounced in FCG cats (mean = 83,244, range: 0-155,074) than in wt cats (mean = 117,045, range: 97,373-132,972). In general, RGC soma counts were lower in FCG cats than they were in wt cats. RGC axon counts in the optic nerve cross-sections were lower than, but strongly correlated to, the total RGC soma count across all cats (in wt and FCG retinas; R2 = 0.88) and solely FCG eyes (R2 = 0.92). The k-means cluster algorithm indicated a region of the greatest mean difference between the normal wt retinas and FCG-affected retinas within the temporal retina, incorporating the region of the area centralis.
CONCLUSIONS: As in other species, RGC soma count and topography are heterogeneous between individual cats, but we identified an ROI in the temporal retina for future studies of RGC soma loss or preservation in a large-eyed model of congenital glaucoma. Many of the methods refined and established to facilitate studies in this FCG model will be broadly applicable to studies in other large-eyed models.
Clinical and pathologic evaluation of chorioretinal lesions in wild owl species
Vet Ophthalmol. 2022 Mar;25(2):128-139. doi: 10.1111/vop.12942. Epub 2021 Sep 29.
OBJECTIVE: Investigate histopathology and spectral-domain optical coherence tomography (OCT) imaging of wild owls with chorioretinitis and identify any potential correlation with an infectious etiology.
MATERIALS AND METHODS: Ophthalmic examination and retinal OCT imaging were performed on fifteen great horned (Strix varia) and barred (Bubo virginianus) owls (30 eyes) with chorioretinitis and five owls with normal eyes (10 eyes). Testing to investigate the presence of potential infectious diseases included a complete blood count, biochemistry, protein electrophoresis, West Nile virus (WNV) plaque reduction neutralization test, Toxoplasma gondii modified direct agglutination test, WNV RT-PCR, and Avian Influenza RT-PCR. A necropsy was performed on all owls, including ocular histopathology.
RESULTS: Fundus lesions included retinal detachment (7/15 owls), depigmented lesions (12/15), pigment clumping (8/15), and retinal tear (4/15). All birds were negative for WNV and Avian Influenza on RT-PCR. Of the owls with chorioretinitis, 3/15 were seropositive for WNV and 7/15 for T. gondii. Optical coherence tomography of 25/30 affected eyes revealed outer retinal lesions (19/25 eyes), retinal detachment (16/25), and retinal tears (3/25). Histopathological examination revealed outer nuclear layer atrophy (19/30 eyes), retinal detachment (18/30), retinal tears (7/30), suprachoroidal hemorrhage (12/30), scleral rupture (3/30), and ossicle fracture (3/30).
CONCLUSIONS: Although 20% of birds were seropositive for WNV and 46.6% for T. gondii, histopathologic findings supported that the posterior segment lesions in the study group were likely due to blunt ocular trauma rather than an infectious etiology. The results of OCT imaging and histopathology documented retinal changes most consistent with blunt ocular trauma.
Development and validation of methods to visualize conventional aqueous outflow pathways in canine primary angle closure glaucoma
Vet Ophthalmol. 2022 May;25 Suppl 1(Suppl 1):84-95. doi: 10.1111/vop.12943. Epub 2021 Sep 28.
PURPOSE: Angle closure glaucoma (PACG) is highly prevalent in dogs and is often refractory to medical therapy. We hypothesized that pathology affecting the post-trabecular conventional aqueous outflow pathway contributes to persistent intraocular pressure (IOP) elevation in dogs with PACG. The goal of this study was to determine the potential for aqueous angiography (AA) and optical coherence tomography (OCT) to identify abnormalities in post-trabecular aqueous outflow pathways in canine PACG.
METHODS: AA and anterior segment OCT (Spectralis HRA + OCT) were performed ex vivo in 19 enucleated canine eyes (10 normal eyes and 9 irreversibly blind eyes from canine patients enucleated for management of refractory PACG). Eyes were cannulated and maintained at physiologic IOP (10-20 mmHg) prior to intracameral infusion of fluorescent tracer. OCT scleral line scans were acquired in regions of high and low perilimbal AA signal. Eyes were then perfusion fixed and cryosections prepared from 10/10 normal and 7/9 PACG eyes and immunolabeled for a vascular endothelial marker.
RESULTS: Normal canine eyes showed segmental, circumferential limbal AA signal, whereas PACG eyes showed minimal or no AA signal. AA signal correlated with scleral lumens on OCT in normal dogs, but lumens were generally absent or flattened in PACG eyes. Collapsed vascular profiles were identified in tissue sections from PACG eyes, including those in which no lumens were identified on AA and OCT.
CONCLUSIONS: In canine eyes with PACG, distal aqueous outflow channels are not identifiable by AA, despite normalization of their IOP, and intra-scleral vascular profiles are collapsed on OCT and histopathology.
Atypical free-floating iridociliary pigmented epithelial cysts and secondary glaucoma in a caiman (Caiman latirostris)
Vet Ophthalmol. 2021 Jul;24(4):414-418. doi: 10.1111/vop.12870. Epub 2021 Feb 16.
We describe a case of chronic ocular trauma that resulted in fixed and free-floating, pigmented epithelial iridociliary cysts, inflammation, and secondary glaucoma in a caiman (Caiman latirostris). A 20- to 25-year-old male caiman was presented with phthisis bulbi in the right eye, and congested episcleral vessels, corneal leukoma, disorganized anterior chamber, multifocal anterior synechia, and elevated intraocular pressure in the left eye. Ocular ultrasound of the left eye revealed round structures dispersed in the anterior and posterior chambers and vitreous cavity. Bilateral enucleation was performed, and gross pathology of the left eye revealed multiple pigmented cysts attached to the iris and posterior corneal surface causing marked distortion of the anterior uvea, and free-floating in the vitreous cavity. Histopathology demonstrated heavily pigmented cystic structures of iridociliary epithelium origin carpeting the anterior segment surfaces and causing obstruction of the iridocorneal angles, leading to secondary glaucoma. To the authors' knowledge, this is the first report of iridociliary cysts in wildlife species.
Ocular porcupine quilling in dogs: Gross, clinical and histopathologic findings in 17 cases (1986-2018)
Vet Ophthalmol. 2021 Mar;24(2):114-124. doi: 10.1111/vop.12851. Epub 2020 Dec 17.
The objectives of this retrospective study were to evaluate the histopathologic changes associated with porcupine ocular quill injuries in dogs, to discuss the various methods of quill detection when quills are not grossly visible, and to discuss the pathogenesis of delayed ocular quill injuries in dogs. Seventeen globes sustaining ocular quilling injuries from 17 dogs (1986-2018) were identified in the COPLOW archives and the gross and histologic changes tabulated and compared. All cases were dogs, with one whole globe submitted from each patient. Sixteen of 17 cases had known or suspected porcupine encounters in the weeks or years preceding enucleation. Histopathologic findings included retinal detachment, hyphema, cataract, granulomatous to pyogranulomatous inflammation (uveitis, endophthalmitis, panophthalmitis), lens capsule rupture, suppurative phakitis, scleral perforation, stromal keratitis, breaks in Descemet's membrane, preiridal fibrovascular membrane, anterior and posterior synechia, Schnabel's cavernous atrophy, and periorbital fibrosis. Quill-associated ocular trauma can have a significant deleterious effect on vision and result in enucleation. The time from initial quilling to the manifestation of ocular signs may be prolonged (weeks to years). Any dog presenting for ocular signs with a history of a previous porcupine encounter should be carefully checked for quill migration into the globe as the source of ocular disease. Quills may not be visible grossly, and ancillary imaging techniques can be utilized with various rates of success.
Microstructure and resident cell-types of the feline optic nerve head resemble that of humans
Exp Eye Res. 2021 Jan;202:108315. doi: 10.1016/j.exer.2020.108315. Epub 2020 Oct 19.
The lamina cribrosa (LC) region of the optic nerve head (ONH) is considered a primary site for glaucomatous damage. In humans, biology of this region reflects complex interactions between retinal ganglion cell (RGC) axons and other resident ONH cell-types including astrocytes, lamina cribrosa cells, microglia and oligodendrocytes, as well as ONH microvasculature and collagenous LC beams. However, species differences in the microanatomy of this region could profoundly impact efforts to model glaucoma pathobiology in a research setting. In this study, we characterized resident cell-types, ECM composition and ultrastructure in relation to microanatomy of the ONH in adult domestic cats (Felis catus). Longitudinal and transverse cryosections of ONH tissues were immunolabeled with astrocyte, microglia/macrophage, oligodendrocyte, LC cell and vascular endothelial cell markers. Collagen fiber structure of the LC was visualized by second harmonic generation (SHG) with multiphoton microscopy. Fibrous astrocytes form glial fibrillary acidic protein (GFAP)-positive glial columns in the pre-laminar region, and cover the collagenous plates of the LC region in lamellae oriented perpendicular to the axons. GFAP-negative and alpha-smooth muscle actin-positive LC cells were identified in the feline ONH. IBA-1 positive immune cells and von Willebrand factor-positive blood vessel endothelial cells are also identifiable throughout the feline ONH. As in humans, myelination commences with a population of oligodendrocytes in the retro-laminar region of the feline ONH. Transmission electron microscopy confirmed the presence of capillaries and LC cells that extend thin processes in the core of the collagenous LC beams. In conclusion, the feline ONH closely recapitulates the complexity of the ONH of humans and non-human primates, with diverse ONH cell-types and a robust collagenous LC, within the beams of which, LC cells and capillaries reside. Thus, studies in a feline inherited glaucoma model have the potential to play a key role in enhancing our understanding of ONH cellular and molecular processes in glaucomatous optic neuropathy.
Prophylactic anti-glaucoma therapy in dogs with primary glaucoma: A practitioner survey of current medical protocols
Vet Ophthalmol. 2021 Mar;24 Suppl 1:96-108. doi: 10.1111/vop.12820. Epub 2020 Sep 12.
AIM: To examine the use of prophylactic anti-glaucoma medications in the normotensive fellow eye in dogs with unilateral overt primary glaucoma by veterinary ophthalmology clinicians.
METHODS: A survey of veterinary ophthalmology clinicians was distributed over two international list serves servicing veterinary ophthalmologists, trainees, and individuals whose practice consisted primarily of ophthalmic patients. The survey was developed following analysis of historical and currently available medical options for control of intraocular pressure and for neuroprotection.
RESULTS: Responses from 199 veterinary ophthalmology clinicians were evaluated. While a large variety of topical anti-hypertensive drugs and protocols were used, the most commonly used medications were aqueous humor production suppressors such as dorzolamide 2.0% ophthalmic solution, timolol 0.5% ophthalmic solution, and a combination product containing both drugs. Latanoprost 0.005% ophthalmic solution was used infrequently for prophylaxis by comparison. The majority of respondents do not use concurrent anti-inflammatory medications (61.22%), although a sizeable minority used prednisolone acetate, dexamethasone, or ketorolac as prophylactic treatment. Systemically administered ocular anti-hypertensive agents were rarely used. Only 40% of respondents used neuroprotectant agents; the most commonly prescribed were the calcium channel blocker amlodipine and the nutraceutical Ocu-Glo™. Recommended intervals between re-examination by the clinician ranged from one month to one year, with most re-evaluations occurring every 3 to 6 months. The majority of respondents recommended more frequent assessments of IOP at intervals between once monthly and once every 3 months.
CONCLUSIONS: Data analysis of medical therapy for the normotensive fellow eye of dogs previously diagnosed with primary glaucoma suggests that there is a great need for well-designed, prospective, controlled, multi-center studies to determine which protocols have the greatest efficacy in delaying an overt attack in the previously normotensive eye in dogs with a genetic predisposition to glaucoma. Prospective studies utilizing a carbonic anhydrase inhibitor such as dorzolamide and a prostaglandin analogue such as latanoprost would be reasonable as these two drugs are widely used in the treatment of overt glaucoma and would allow for an exploration of the impact of different mechanisms of action of lowering IOP on the pathophysiology of primary glaucoma.
Safety and Biocompatibility of Aflibercept-Loaded Microsphere Thermo-Responsive Hydrogel Drug Delivery System in a Nonhuman Primate Model
Transl Vis Sci Technol. 2020 Feb 27;9(3):30. doi: 10.1167/tvst.9.3.30.
PURPOSE: To evaluate the safety and tolerability of a microsphere thermo-responsive hydrogel drug delivery system (DDS) loaded with aflibercept in a nonhuman primate model.
METHODS: A sterile 50 µL of aflibercept-loaded microsphere thermo-responsive hydrogel-DDS (aflibercept-DDS) was injected intravitreally into the right eye of 10 healthy rhesus macaques. A complete ophthalmic examination, intraocular pressure (IOP) measurement, fundus photography, spectral-domain optical coherence tomography (SD-OCT), and electroretinogram were performed monthly for 6 months. One macaque was euthanized monthly, and the enucleated eyes were submitted for measurement of bioactive aflibercept concentrations. Four eyes were submitted for histopathology.
RESULTS: Injected aflibercept-DDS was visualized in the vitreous until 6 months postinjection. No abnormalities were observed in the anterior segment, and IOP remained within normal range during the study period. A small number of cells were observed in the vitreous of some macaques, but otherwise the remainder of the posterior segment examination was normal. No significant changes in retinal architecture or function as assessed by SD-OCT and histology or full-field electroretinography, respectively, were observed. A mild, focal foreign body reaction around the injectate was observed with histology at 6 months postinjection. A mean of 2.1 ng/µL of aflibercept was measured in the vitreous.
CONCLUSIONS: Intravitreally injected aflibercept-DDS achieved controlled, sustained release of aflibercept with no adverse effects for up to 6 months in the eyes of healthy rhesus macaques.
TRANSLATIONAL RELEVANCE: Aflibercept-DDS may be a more effective method to deliver bioactive antivascular endothelial growth factor agents than current practice by reducing the frequency of intravitreal injections and providing controlled drug release.
Targeted deletion of Cyp1b1 in pericytes results in attenuation of retinal neovascularization and trabecular meshwork dysgenesis
Trends Dev Biol. 2019;12:1-12.
Mutations in cytochrome P450 1B1 (CYP1B1) gene are reported in patients with primary congenital glaucoma. Cyp1b1-deficient (Cyp1b1-/-) mice show dysgenesis of the trabecular meshwork (TM) tissue and attenuation of retinal neovascularization during oxygen-induced ischemic retinopathy (OIR). Although retinal vascular cells, including endothelial cells (EC), pericytes (PC), astrocytes (AC), and TM endothelial cells express CYP1B1, the cell autonomous contribution of CYP1B1 to attenuation of retinal neovascularization and TM tissue dysgenesis remains unknown. Here we determined the impact lack of CYP1B1 expression in EC, PC or AC has on retinal neovascularization and TM tissue integrity. We generated Cyp1b1-transgenic mice with vascular cell-specific targeted Cre+-deletion in EC (Cyp1b1 EC), in PC (Cyp1b1 PC) and in AC (Cyp1b1 AC). Pathologic retinal neovascularization during OIR was evaluated by collagen IV staining of retinal wholemounts. Structural morphology of TM tissue was examined by transmission electron microscopy (TEM). The assessment of retinal neovascularization indicated a significant decrease in retinal neovascular tufts only in Cyp1b1 PC mice compared with control mice. TEM evaluation demonstrated Cyp1b1 PC mice also exhibited a defect in TM tissue morphology and integrity similar to that reported in Cyp1b1-/- mice. Thus, Cyp1b1 expression in PC plays a significant role in retinal neovascularization and the integrity of TM tissue.
Sub-region-Specific Optic Nerve Head Glial Activation in Glaucoma
Mol Neurobiol. 2020 Jun;57(6):2620-2638. doi: 10.1007/s12035-020-01910-9. Epub 2020 Apr 7.
Glaucoma, a multifactorial neurodegenerative disease characterized by progressive loss of retinal ganglion cells and their axons in the optic nerve, is a leading cause of irreversible vision loss. Intraocular pressure (IOP) is a risk factor for axonal damage, which initially occurs at the optic nerve head (ONH). Complex cellular and molecular mechanisms involved in the pathogenesis of glaucomatous optic neuropathy remain unclear. Here we define early molecular events in the ONH in an inherited large animal glaucoma model in which ONH structure resembles that of humans. Gene expression profiling of ONH tissues from rigorously phenotyped feline subjects with early-stage glaucoma and precisely age-matched controls was performed by RNA-sequencing (RNA-seq) analysis and complementary bioinformatic approaches applied to identify molecular processes and pathways of interest. Immunolabeling supported RNA-seq findings while providing cell-, region-, and disease stage-specific context in the ONH in situ. Transcriptomic evidence for cell proliferation and immune/inflammatory responses is identifiable in early glaucoma, soon after IOP elevation and prior to morphologically detectable axon loss, in this large animal model. In particular, proliferation of microglia and oligodendrocyte precursor cells is a prominent feature of early-stage, but not chronic, glaucoma. ONH microgliosis is a consistent hallmark in both early and chronic stages of glaucoma. Molecular pathways and cell type-specific responses strongly implicate toll-like receptor and NF-κB signaling in early glaucoma pathophysiology. The current study provides critical insights into molecular pathways, highly dependent on cell type and sub-region in the ONH even prior to irreversible axon degeneration in glaucoma.
Management of corneal epithelial defects in a population of mature chuck-will's-widows (Antrostomus carolinensis) in South Florida
Vet Ophthalmol. 2020 May;23(3):567-574. doi: 10.1111/vop.12753. Epub 2020 Feb 26.
PURPOSE: To describe ocular clinical findings, gross/histopathologic findings, and treatment regimens in a series of migratory chuck-will's-widows (Antrostomus carolinensis) (CWW) with corneal epithelial defects.
METHODS: Seven CWW were presented to the South Florida Wildlife Center (SFWC). Four presented with bilateral (OU) corneal ulceration; two developed corneal ulceration OU; one had no ocular lesions. Treatment protocols for patients with corneal ulcers included the following: medical therapy only or medical therapy combined with an additional procedure. Four patients including the bird with no ocular lesions were euthanized, and one patient died. Their globes were submitted for histopathology. Two patients were released.
RESULTS: Clinical findings prior to enucleation included superficial corneal ulceration with redundant epithelium persisting weeks to >1 month. On histopathology, epithelium in nonulcerated globes was remarkably thin; this was considered normal. Common histopathologic findings of ulcerated globes revealed epithelial and conjunctival attenuation with an acellular superficial stromal layer and hypercellular mid-stromal layer. One globe healed with medical therapy and cotton tip applicator debridement. Four globes healed by combination of medical therapy, equine amnion, nictitating membrane (NM) flap, and temporary tarsorrhaphy. No globes healed with diamond burr debridement or grid keratotomy.
CONCLUSIONS: Factors that may be contributing to these corneal epithelial defects include, but are not limited to, normally thin epithelium, exposure keratopathy, neurotrophic disease, epithelial turnover and inadequate stem cell recruitment, inherited/genetic causes, and unidentified infectious agents (eg, viral etiologies). Of the 12 eyes treated, one healed with medical therapy/cotton tip applicator debridement, and four healed with medical therapy/equine amnion/nictitating membrane flap/temporary tarsorrhaphy.
A novel cellular structure in the retina of insectivorous birds
Sci Rep. 2019 Oct 23;9(1):15230. doi: 10.1038/s41598-019-51774-w.
The keen visual systems of birds have been relatively well-studied. The foundations of avian vision rest on their cone and rod photoreceptors. Most birds use four cone photoreceptor types for color vision, a fifth cone for achromatic tasks, and a rod for dim-light vision. The cones, along with their oil droplets, and rods are conserved across birds - with the exception of a few shifts in spectral sensitivity - despite taxonomic, behavioral and ecological differences. Here, however, we describe a novel photoreceptor organelle in a group of New World flycatchers (Empidonax spp.) in which the traditional oil droplet is replaced with a complex of electron-dense megamitochondria surrounded by hundreds of small, orange oil droplets. The photoreceptors with this organelle were unevenly distributed across the retina, being present in the central region (including in the fovea), but absent from the retinal periphery and the area temporalis of these insectivorous birds. Of the many bird species with their photoreceptors characterized, only the two flycatchers described here (E. virescens and E. minimus) possess this unusual retinal structure. We discuss the potential functional significance of this unique sub-cellular structure, which might provide an additional visual channel for these small predatory songbirds.
Imaging Distal Aqueous Outflow Pathways in a Spontaneous Model of Congenital Glaucoma
Transl Vis Sci Technol. 2019 Oct 9;8(5):22. doi: 10.1167/tvst.8.5.22. eCollection 2019 Sep.
PURPOSE: To validate the use of aqueous angiography (AA) in characterizing distal aqueous outflow pathways in normal and glaucomatous cats.
METHODS: Ex vivo AA and optical coherence tomography (OCT) were performed in nine adult cat eyes (5 feline congenital glaucoma [FCG] and 4 normal), following intracameral infusion of 2.5% fluorescein and/or 0.4% indocyanine green (ICG) at physiologic intraocular pressure (IOP). Scleral OCT line scans were acquired in areas of high- and low-angiographic signal. Tissues dissected in regions of high- and low-AA signal, were sectioned and hematoxylin and eosin (H&E)-stained or immunolabeled (IF) for vascular endothelial and perivascular cell markers. Outflow vessel numbers and locations were compared between groups by Student's t-test.
RESULTS: AA yielded circumferential, high-quality images of distal aqueous outflow pathways in normal and FCG eyes. No AA signal or scleral lumens were appreciated in one buphthalmic FCG eye, though collapsed vascular profiles were identified on IF. The remaining eight of nine eyes all showed segmental AA signal, distinguished by differences in time of signal onset. AA signal always corresponded with lumens seen on OCT. Numbers of intrascleral vessels were not significantly different between groups, but scleral vessels were significantly more posteriorly located relative to the limbus in FCG.
CONCLUSIONS: A capacity for distal aqueous humor outflow was confirmed by AA in FCG eyes ex vivo but with significant posterior displacement of intrascleral vessels relative to the limbus in FCG compared with normal eyes.
TRANSLATIONAL RELEVANCE: This report provides histopathologic correlates of advanced diagnostic imaging findings in a spontaneous model of congenital glaucoma.
A clinicopathological study of 17 cases of ocular surface xanthogranuloma in dogs
Vet Ophthalmol. 2020 Jan;23(1):190-198. doi: 10.1111/vop.12711. Epub 2019 Sep 22.
OBJECTIVE: To evaluate the clinical, histopathological, and immunohistochemical features of 17 cases of ocular surface xanthogranuloma (OSX) in dogs.
METHODS: Archived records from the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) were searched for cases of canine OSX. Cases were evaluated for lipid-laden macrophages and Touton giant cells. Seventeen cases matching those criteria were identified (1993-2018). Clinical and epidemiological data were collected from the submission forms and additional follow-up survey.
RESULTS: Ocular surface xanthogranuloma in dogs presented as small bland nodules. OSX commonly occurred at the limbus (8/17) or cornea (4/17). Three of 17 affected animals were less than 1-year-old and the average age was 6.9 years (range 0.7-14 years). Fourteen of 17 cases did not report any lipid or metabolic abnormalities. Histologically, lesions were composed mainly of dense sheets of vacuolated lipid-laden macrophages and Touton giant cells with scant additional inflammatory cells and an intact overlying epithelium. No recurrence was noted in cases where complete surgical resection was achieved, and medical treatment either pre or post-resection led to only partial resolution.
CONCLUSIONS: Xanthogranulomas are histiocytic lesions characterized by abundant lipid-laden macrophages. The authors use the term, ocular surface xanthogranuloma, to describe nodules with rigidly defined cellular characteristics. Although these lesions share characteristics with human limbal xanthogranulomas, further investigation is needed to suggest the different subsets that have been reported in the medical literature. Complete surgical excision is the most effective treatment for OSX in dogs, and intralesional triamcinolone and topical steroids can be useful adjunctive therapies to surgery.
Cactus-induced keratoconjunctivitis in Texas: A case series of three dogs and one cat
Vet Ophthalmol. 2020 Mar;23(2):374-385. doi: 10.1111/vop.12712. Epub 2019 Sep 22.
OBJECTIVE: To describe the historical, clinical, and diagnostic features of small animal patients affected by cactus-induced keratoconjunctivitis and their response to therapy.
ANIMALS STUDIED: Three dogs and one cat.
PROCEDURES: Ophthalmic examination directed subsequent selected diagnostic tests in each case including light microscopy of extracted foreign bodies, in vivo confocal microscopy (IVCM), corneal histopathology, and corneal bacterial culture. Treatments consisted of foreign body surgical extraction with concurrent medical therapy (three cases), or medical therapy alone (one case).
RESULTS: Clinical histories obtained supported acute cactus injury in all cases. Ophthalmic abnormalities were unilateral in each case and included ulcerative keratoconjunctivitis associated with linear, microscopic conjunctival and/or corneal penetrating cactus spines, known as glochids. Light microscopy and IVCM showed glochids to be heavily barbed, consistent with the spine morphology Prickly Pear (Opuntia) cactus species. Bacterial culture yielded Proprionicimonas sp. in one case with keratomalacia. Surgical extraction of spines was challenging, and residual conjunctival and/or corneal glochids were present in all cases. Patient discomfort resolved at a median of 21 days (range 10-51 days). Vision-threatening complications were not observed in any case at the time of last follow-up examination. Epithelial downgrowth, demonstrated by IVCM and histopathology, was present in one case at 108-day follow-up.
CONCLUSIONS: Cactus-induced keratoconjunctivitis should be considered as a differential in regions in which Opuntia cacti are prevalent, and microscopic ocular foreign bodies are observed. Although glochids are difficult to extract, positive clinical outcomes can occur in small animal patients despite the presence of residual organic corneal foreign material.
Clinical and histopathological classification of feline intraocular lymphoma
Vet Ophthalmol. 2020 Jan;23(1):77-89. doi: 10.1111/vop.12692. Epub 2019 Jul 22.
This retrospective study aimed to describe and classify cats with intraocular lymphoma, determine the proportion of cases with presumed solitary ocular lymphoma (PSOL) compared with ocular manifestations of multicentric disease and assess the clinical outcomes of these patients. One hundred seventy-two cases identified through biopsy submissions were reviewed histologically; 163 of these cases were subtyped according to the WHO classification system. Cases were categorized as having PSOL or ocular lymphoma with suspected systemic involvement (SSI) based on submission forms and follow-up data. The majority of cases exhibited concurrent uveitis (75%) and secondary glaucoma (58%). Diffuse large B-cell lymphoma was the most common subtype (n = 86; 53%), followed by peripheral T-cell lymphoma (n = 44; 27%). Other subtypes included anaplastic large T- (n = 8; 5%) and B-cell (n = 4; 2.5%) lymphomas, and 15 cases (9%) were negative for all immunohistochemical markers. In sixty-nine cases (40%), adequate clinical data and sufficient survival data were obtained to distinguish PSOL from SSI. PSOL comprised the majority of cases (64%), while 36% had SSI. When covarying for age at diagnosis, the median survival time was significantly higher (P = 0.003) for cases of PSOL (154 days) versus those with SSI (69 days); hazards ratio of 0.47 for PSOL (95% CI: 0.241-0.937). The subtype of lymphoma did not affect survival time. Cats with PSOL represent a greater proportion of the disease population, and this subset of cats with intraocular lymphoma has a better clinical outcome.
Bilateral Anterior Uveitis in a Northern Saw-whet Owl (<em>Aegolius acadicus</em>) With a Metastatic Pectoral Malignant Mesenchymoma
J Avian Med Surg. 2019 Jun 1;33(2):171-178. doi: 10.1647/2017-326.
A captive, adult, male northern saw-whet owl (Aegolius acadicus) was examined for blepharospasm of the left eye. The owl was diagnosed with bilateral anterior uveitis and a corneal ulceration in the left eye. It was treated with oral and topical nonsteroidal anti-inflammatory medications and a topical antibiotic. Multiple recheck examinations and medication adjustments were performed over the next 4 months, at the end of which time the bilateral anterior uveitis was controlled with a topical nonsteroidal anti-inflammatory applied 3 times per week to both eyes. The owl was re-examined 2 months later after 2 suspected neurologic episodes. On physical examination, the owl was quiet and had difficulty standing and ambulating. Five firm multilobular and immobile masses were identified overlying the pectoral muscle and sternum. Fine-needle aspiration from 1 mass revealed neoplastic cells consistent with a sarcoma. The owl was euthanatized. On the basis of results of histopathologic examination, the mass was diagnosed as a pleomorphic spindle cell sarcoma with features of rhabdomyosarcoma, liposarcoma, and osteosarcoma. Numerous tumor cells were immunopositive for myoglobin and desmin, indicating striated muscle origin. Although a metastatic lesion was present in 1 adrenal gland, lesions of inflammation or neoplasia were absent in either eye on histopathologic examination. This report describes an apparent ocular manifestation of systemic disease in an avian species with clinically diagnosed recurrent anterior uveitis.
The future of canine glaucoma therapy
Vet Ophthalmol. 2019 Sep;22(5):726-740. doi: 10.1111/vop.12678. Epub 2019 May 20.
Canine glaucoma is a group of disorders that are generally associated with increased intraocular pressure (IOP) resulting in a characteristic optic neuropathy. Glaucoma is a leading cause of irreversible vision loss in dogs and may be either primary or secondary. Despite the growing spectrum of medical and surgical therapies, there is no cure, and many affected dogs go blind. Often eyes are enucleated because of painfully high, uncontrollable IOP. While progressive vision loss due to primary glaucoma is considered preventable in some humans, this is mostly not true for dogs. There is an urgent need for more effective, affordable treatment options. Because newly developed glaucoma medications are emerging at a very slow rate and may not be effective in dogs, work toward improving surgical options may be the most rewarding approach in the near term. This Viewpoint Article summarizes the discussions and recommended research strategies of both a Think Tank and a Consortium focused on the development of more effective therapies for canine glaucoma; both were organized and funded by the American College of Veterinary Ophthalmologists Vision for Animals Foundation (ACVO-VAF). The recommendations consist of (a) better understanding of disease mechanisms, (b) early glaucoma diagnosis and disease staging, (c) optimization of IOP-lowering medical treatment, (d) new surgical therapies to control IOP, and (e) novel treatment strategies, such as gene and stem cell therapies, neuroprotection, and neuroregeneration. In order to address these needs, increases in research funding specifically focused on canine glaucoma are necessary.
Description of an ultrasound-guided erector spinae plane block and the spread of dye in dog cadavers
Vet Anaesth Analg. 2019 Jul;46(4):516-522. doi: 10.1016/j.vaa.2019.03.002. Epub 2019 Mar 27.
OBJECTIVES: To describe a technique to perform an ultrasound-guided erector spinae plane (ESP) block and determine the distribution and potential complications after injection of two volumes of methylene blue in dog cadavers.
STUDY DESIGN: Prospective experimental cadaveric study.
ANIMALS: A total of eight dog cadavers weighing 9.3 ± 1.9 kg.
METHODS: Ultrasound-guided injections dorsal to the transverse process and ventral to the erector spinae muscles aimed at the fifth thoracic transverse process were performed bilaterally in each dog using 0.5 and 1.0 mL kg-1 dye solution [low volume (LV) and high volume (HV) treatments, respectively]. Treatments were randomly assigned to the right or left side of each dog, resulting in a total of 16 injections. Anatomical dissections determined dye spread characteristics, including epaxial muscles spread, staining of spinal nerves, dorsal rami, ventral rami (intercostal nerves) and sympathetic trunk spread. Staining indicating potential complications (epidural, mediastinal and intrapleural spread) was recorded.
RESULTS: There was complete staining of at least one dorsal ramus following all injections. A more extensive spread was observed along the muscles in the HV compared with LV (p = 0.036). No significant difference between multisegmental dorsal rami spread (six out of eight injections in each treatment) was noted. Out of 16 injections, one in LV treatment resulted in multisegmental spinal nerve staining and one in HV treatment resulted in ventral ramus (intercostal nerve) staining. Use of anatomic landmarks resulted in inaccurate identification of the fifth transverse process in at least six out of 16 injections (38%). No sympathetic trunk, epidural, mediastinal or intrapleural staining was observed.
CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasound-guided ESP injections resulted in extensive staining along the epaxial muscles, as well as staining of the dorsal rami in all dogs. The incidence of dorsal rami mutisegmental spread was the same in both treatments.
Ocular phenotypic consequences of a single copy deletion of the <em>Yap1</em> gene (<em>Yap1</em> <sup>+/-</sup>) in mice
Mol Vis. 2019 Feb 17;25:129-142. eCollection 2019.
PURPOSE: To identify the effects of a single copy deletion of Yap1 (Yap1 +/-) in the mouse eye, the ocular phenotypic consequences of Yap1 +/- were determined in detail.
METHODS: Complete ophthalmic examinations, as well as corneal esthesiometry, the phenol red thread test, intraocular pressure, and Fourier-domain optical coherence tomography were performed on Yap1 +/- and age-matched wild-type (WT) mice between eyelid opening (2 weeks after birth) and adulthood (2 months and 1 year after birth). Following euthanasia, enucleated eyes were characterized histologically.
RESULTS: Microphthalmia with small palpebral fissures, corneal fibrosis, and reduced corneal sensation were common findings in the Yap1 +/- mice. Generalized corneal fibrosis precluded clinical examination of the posterior structures. Histologically, thinning and keratinization of the corneal epithelium were observed in the Yap1 +/- mice in comparison with the WT mice. Distorted collagen fiber arrangement and hypercellularity of keratocytes were observed in the stroma. Descemet's membrane was extremely thin and lacked an endothelial layer in the Yap1 +/- mice. The iris was adherent to the posterior cornea along most of its surface creating a distorted contour. Most of the Yap1 +/- eyes were microphakic with swollen fibers and bladder cells. The retinas of the Yap1 +/- mice were normal at 2 weeks and 2 months of age, but the presence of retinal abnormalities, including retinoschisis and detachment, was markedly increased in the Yap1 +/- mice at 1 year of age.
CONCLUSIONS: The results show that the heterozygous deletion of the Yap1 gene in mice leads to complex ocular abnormalities, including microphthalmia, corneal fibrosis, anterior segment dysgenesis, and cataract.
Canine ocular and periocular snakebites requiring enucleation: A report of 19 cases
Vet Ophthalmol. 2019 Sep;22(5):666-673. doi: 10.1111/vop.12638. Epub 2019 Feb 4.
PURPOSE: To describe the clinical and histopathologic features secondary to ocular and periocular snakebites in dogs requiring enucleation.
METHODS: Retrospective review of patients with recorded snakebite envenomation from the archives of the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) and Texas A&M Veterinary Medical Teaching Hospital (1997-2017). The cases included in this study required witnessed snakebites to the dog by the owner, clinical signs supportive of periocular or ocular envenomation, and/or histopathologic lesions compatible with snakebites. Two groups were established: ocular bites (OB) and periocular bites (PB).
RESULTS: Nineteen cases were included in the study (OB = 16/19; PB = 3/19). Dogs affected were typically older (median 8 years; range 1-18), and both sexes were equally represented. Left eyes (14/19) were more likely to sustain snake-induced trauma compared to right eyes (5/19). Fifteen breeds were identified, with terriers (9/19) commonly represented. Snakes bites occurred in six US states, with the majority of cases from Texas (7/19), California (5/19), and Arizona (4/19). Common clinical signs included facial edema, corneal ulceration, keratomalacia, uveitis, hyphema, and secondary glaucoma. All eyes demonstrated vision loss prior to enucleation. Histologically, the ocular and periocular tissues contained extensive necrosis associated with envenomation. Retinal detachment, lens capsule rupture, and intraocular hemorrhage/inflammation were commonly found.
CONCLUSIONS: Snakebite envenomation is a largely necrotizing disease process that can result in profound infiltrative and destructive ocular changes presumed to be related to the proteolytic factors and necrotoxins in venom. Ocular alterations secondary to snakebites may be irreversible regardless of supportive therapy instituted.
PRESUMED PHOTORECEPTOR DYSPLASIAS IN PEREGRINE FALCONS ( FALCO PEREGRINUS) AND PEREGRINE FALCON HYBRIDS
J Wildl Dis. 2019 Apr;55(2):325-334. doi: 10.7589/2018-02-055. Epub 2018 Oct 2.
We describe a case series of photoreceptor dysplasia with secondary retinal degeneration in juvenile Peregrine Falcons. Six Peregrine Falcons ( Falco peregrinus) and three Peregrine Falcon × Prairie Falcon ( Falco mexicanus) hybrids had early-life visual deficits. Eight birds had visual defects shortly after hatching, and one bird had visual deficits first noticed at 5 mo of age. Complete ophthalmic examinations were performed in each animal. Eight of the animals had electroretinograms, and nine of the animals had their eyes examined histologically after euthanasia. Ophthalmic examinations did not reveal consistent and potentially blinding abnormalities, including an absence of ophthalmoscopic retinal lesions. Electroretinographic findings included subnormal amplitudes (with rod responses more abnormal than cone responses), with a negative b-wave amplitude occurring in one bird. Histologically, a reduction in the number of photoreceptors was present with numerous degenerative changes to the remaining photoreceptors, including frequent blunting and disorganization of photoreceptor outer segments, decreased numbers of cells in the inner nuclear layer, decreased numbers of ganglion cells, decreased thickness of the nerve fiber layer, and decreased myelinated axons within the optic nerve. Ultrastructurally, only minor cone outer segment changes and occasional phagocytic cells were seen. Results strongly suggested a primary retinopathy, characterized by photoreceptor dysplasia and secondary retinal degeneration with loss of cellular elements throughout the retina. The presence of a similar spectrum of findings in related individuals, the early age of onset, and the relative lack of other environmental, ocular, or systemic abnormalities suggested possible heritability.
Cyp1b1 expression impacts the angiogenic and inflammatory properties of liver sinusoidal endothelial cells
PLoS One. 2018 Oct 29;13(10):e0206756. doi: 10.1371/journal.pone.0206756. eCollection 2018.
Cytochrome P450 1B1 (CYP1B1) is a member of the cytochrome p450 family of enzymes that catalyze mono-oxygenase reactions. Although constitutive Cyp1b1 expression is limited in hepatocytes, its expression and function in liver sinusoidal endothelial cells (LSEC) remains unknown. Here we determined the impact of Cyp1b1 expression on LSEC properties prepared from Cyp1b1+/+ and Cyp1b1-/- mice. LSEC expressed PECAM-1, VE-cadherin, and B4 lectin similar to EC from other mouse tissues. Cyp1b1 +/+ LSEC constitutively expressed significant levels of Cyp1b1, while Cyp1b1-/- LSEC lacked Cyp1b1 expression. LSEC also expressed VEGFR3, PROX-1, and LYVE-1, VEGFR1 and VEGFR2, as well as other cell adhesion molecules including ICAM-1, ICAM-2, VCAM-1, and thrombospondin-1 (TSP1) receptors, CD36 and CD47. However, the expression of PV-1 and stabilin (fenestration markers), and endoglin were limited in these cells. The Cyp1b1-/- LSEC showed limited fenestration, and decreased levels of VEGF and BMP6. Cyp1b1-/- LSEC also showed a decrease in the levels of VE-cadherin and ZO-1 impacting adherens and gap junction formation. Cyp1b1-/- LSEC were significantly more apoptotic, proliferated at a faster rate, and were less adherent and more migratory. These changes were attributed, in part, to decreased amounts of TSP1 and increased AKT and ERK activation. The expressions of integrins were also altered by the lack of Cyp1b1, but the ability of these cells to undergo capillary morphogenesis was minimally affected. Furthermore, Cyp1b1-/- LSEC expressed lower levels of inflammatory mediators MCP-1 and TNF-α. Thus, Cyp1b1 expression has a significant impact on LSEC angiogenic and inflammatory functions.
Description of an ultrasound-guided thoracic paravertebral block technique and the spread of dye in dog cadavers
Vet Anaesth Analg. 2018 Nov;45(6):811-819. doi: 10.1016/j.vaa.2018.07.004. Epub 2018 Aug 10.
OBJECTIVES: To describe an ultrasound-guided thoracic paravertebral block and determine the distribution after injection of two volumes of methylene blue in dog cadavers.
STUDY DESIGN: Prospective experimental cadaveric study.
ANIMALS: Twelve dog cadavers weighing 11 ± 3 kg.
METHODS: Ultrasound-guided injections aimed at the fifth thoracic (T5) paravertebral space were performed in randomized order using 0.1 or 0.3 mL kg-1 dye solution (six dogs for each volume). Anatomic dissections determined dye spread characteristics, including the presence and degree of staining of spinal nerves, and the presence of intercostal and sympathetic trunk spread. Staining of mediastinum, epidural, intrapleural and contralateral thoracic paravertebral space was recorded.
RESULTS: There was no significant difference in dye distribution between groups. The use of anatomic landmarks resulted in the inaccurate identification of the T5 paravertebral space. The T4, T5 and T6 paravertebral spaces were injected in four, five and three of 12 dogs, respectively. Complete staining of the spinal nerve of the thoracic paravertebral space injected was observed in 11 of 12 dogs, and partial staining in one dog in the low-volume group. Multisegmental distribution was demonstrated with staining of contiguous spinal nerves in one dog in the high-volume group, and multiple segments of intercostal (three dogs) and sympathetic trunk (four dogs) spread in both groups. No mediastinal, epidural, intrapleural or contralateral thoracic paravertebral space staining was observed.
CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasound-guided injection at the thoracic paravertebral space resulted in staining of the spinal nerve in all dogs. However, T5 paravertebral space was not accurately identified using anatomic landmarks. Dye distribution was not significantly different between the two groups; therefore, the use of the lower-volume and multiple-site injections would be potentially necessary in clinical cases to achieve ipsilateral blockade of the thoracic wall.
Observational Study Design in Veterinary Pathology, Part 2: Methodology
Vet Pathol. 2018 Nov;55(6):774-785. doi: 10.1177/0300985818798121. Epub 2018 Sep 18.
Observational studies are a basis for much of our knowledge of veterinary pathology, yet considerations for conducting pathology-based observational studies are not readily available. In part 1 of this series, we offered advice on planning and carrying out an observational study. Part 2 of the series focuses on methodology. Our general recommendations are to consider using already-validated methods, published guidelines, data from primary sources, and quantitative analyses. We discuss 3 common methods in pathology research-histopathologic scoring, immunohistochemistry, and polymerase chain reaction-to illustrate principles of method validation. Some aspects of quality control include use of clear objective grading criteria, validation of key reagents, assessing sample quality, determining specificity and sensitivity, use of technical and biologic negative and positive controls, blinding of investigators, approaches to minimizing operator-dependent variation, measuring technical variation, and consistency in analysis of the different study groups. We close by discussing approaches to increasing the rigor of observational studies by corroborating results with complementary methods, using sufficiently large numbers of study subjects, consideration of the data in light of similar published studies, replicating the results in a second study population, and critical analysis of the study findings.
Observational Study Design in Veterinary Pathology, Part 1: Study Design
Vet Pathol. 2018 Sep;55(5):607-621. doi: 10.1177/0300985818785705. Epub 2018 Aug 2.
Observational studies are the basis for much of our knowledge of veterinary pathology and are highly relevant to the daily practice of pathology. However, recommendations for conducting pathology-based observational studies are not readily available. In part 1 of this series, we offer advice on planning and conducting an observational study with examples from the veterinary pathology literature. Investigators should recognize the importance of creativity, insight, and innovation in devising studies that solve problems and fill important gaps in knowledge. Studies should focus on specific and testable hypotheses, questions, or objectives. The methodology is developed to support these goals. We consider the merits and limitations of different types of analytic and descriptive studies, as well as of prospective vs retrospective enrollment. Investigators should define clear inclusion and exclusion criteria and select adequate numbers of study subjects, including careful selection of the most appropriate controls. Studies of causality must consider the temporal relationships between variables and the advantages of measuring incident cases rather than prevalent cases. Investigators must consider unique aspects of studies based on archived laboratory case material and take particular care to consider and mitigate the potential for selection bias and information bias. We close by discussing approaches to adding value and impact to observational studies. Part 2 of the series focuses on methodology and validation of methods.
In vivo confocal microscopy characteristics of equine epithelial and subepithelial nonulcerative keratomycosis
Vet Ophthalmol. 2019 Mar;22(2):168-176. doi: 10.1111/vop.12576. Epub 2018 May 2.
OBJECTIVE: To describe the in vivo confocal microscopy features of horses with epithelial and subepithelial nonulcerative keratomycosis.
ANIMALS STUDIED: Four horses with a clinical diagnosis of epithelial or subepithelial keratomycosis.
PROCEDURES: Horses were examined on one or more occasions by in vivo laser scanning confocal microscopy of the cornea. Confocal microscopic examination characteristics were correlated with clinical, cytological, and histopathological findings for the horses.
RESULTS: All horses had an irregular corneal epithelial surface during slit-lamp biomicroscopy examination. Epithelial or subepithelial corneal opacities were present in multifocal or diffuse patterns. Positive rose bengal corneal staining was present focally or diffusely in all cases. Fungal hyphae were detected in cytological or histopathological corneal samples from all horses. Aspergillus, Fusarium, and Penicillium spp. were cultured from corneal samples. Confocal microscopy detected hyphae diffusely distributed over the axial cornea in horses with epithelial clinical disease. Fungal hyphae were present in all layers of the corneal epithelium and associated with disorganized and sloughing epithelial cells with minimal leukocytes. Subepithelial keratomycosis was correlated with focal, dense accumulations of hyphae in the immediate subepithelial anterior stroma that were surrounded by moderate numbers of leukocytes. Two horses were examined by confocal microscopy on multiple occasions during the course of medical therapy, and fungal hyphae were observed to migrate from the epithelium into the subepithelial stroma as the clinical corneal disease progressed.
CONCLUSIONS: With in vivo confocal microscopy, both epithelial and subepithelial keratomycosis appear as unique clinical entities. Equine epithelial keratomycosis is a potential precursor to subepithelial keratomycosis.
Ocular and uteroplacental pathology in a macaque pregnancy with congenital Zika virus infection
PLoS One. 2018 Jan 30;13(1):e0190617. doi: 10.1371/journal.pone.0190617. eCollection 2018.
Congenital Zika virus (ZIKV) infection impacts fetal development and pregnancy outcomes. We infected a pregnant rhesus macaque with a Puerto Rican ZIKV isolate in the first trimester. The pregnancy was complicated by preterm premature rupture of membranes (PPROM), intraamniotic bacterial infection and fetal demise 49 days post infection (gestational day 95). Significant pathology at the maternal-fetal interface included acute chorioamnionitis, placental infarcts, and leukocytoclastic vasculitis of the myometrial radial arteries. ZIKV RNA was disseminated throughout fetal tissues and maternal immune system tissues at necropsy, as assessed by quantitative RT-PCR for viral RNA. Replicating ZIKV was identified in fetal tissues, maternal uterus, and maternal spleen by fluorescent in situ hybridization for viral replication intermediates. Fetal ocular pathology included a choroidal coloboma, suspected anterior segment dysgenesis, and a dysplastic retina. This is the first report of ocular pathology and prolonged viral replication in both maternal and fetal tissues following congenital ZIKV infection in a rhesus macaque. PPROM followed by fetal demise and severe pathology of the visual system have not been described in macaque congenital ZIKV infection previously. While this case of ZIKV infection during pregnancy was complicated by bacterial infection with PPROM, the role of ZIKV on this outcome cannot be precisely defined, and further nonhuman primate studies will determine if increased risk for PPROM or other adverse pregnancy outcomes are associated with congenital ZIKV infection.
Orbital invasive squamous cell carcinoma with adnexal involvement clinically mimicking feline restrictive orbital myofibroblastic sarcoma: 19 cases (1990-2016)
Vet Ophthalmol. 2018 May;21(3):281-289. doi: 10.1111/vop.12506. Epub 2017 Nov 21.
OBJECTIVE: To describe the clinical presentations of patients diagnosed with ocular adnexal or orbital squamous cell carcinoma (SCC), which possess features similar to feline restrictive orbital myofibroblastic sarcoma (FROMS).
PROCEDURES: A retrospective review of adnexal and/or orbital SCC was performed. Cases were collected from the University of Georgia College of Veterinary Medicine and the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) (1990-2016). Data included signalment, ophthalmic clinical signs, nonophthalmic history and clinical signs, clinician suspicion of FROMS, advanced imaging results, and subsequent histopathologic diagnosis. FROMS cases from the COPLOW over the same time span were reviewed and compared statistically to the SCC cases with a significance threshold of 0.05.
RESULTS: Nineteen cases (20 eyes) were identified with adnexal SCC with features similar to FROMS, including keratitis and eyelid/third eyelid restriction and/or thickening. There were no statistically significant differences between clinical findings in the SCC cases and the identified and compared FROMS cases (57 cases; 67 eyes), except for exophthalmos and/or resistance to retropulsion, which was less common in SCC cases (20%) than in FROMS cases (47.8%) (P = 0.027); and clinical or imaged presence of an overt eyelid or orbital mass, which was more common in the SCC cases (30%) than in the FROMS cases (4.5%) (P = 0.0010).
CONCLUSIONS: SCC with adnexal involvement has many features similar to FROMS. In addition to FROMS, SCC should be considered a differential diagnosis in cats with restrictive adnexal or orbital signs and corneal changes.
Retinal pathology in the PPCD1 mouse
PLoS One. 2017 Oct 5;12(10):e0185094. doi: 10.1371/journal.pone.0185094. eCollection 2017.
Retinal phenotypes of the PPCD1 mouse, a mouse model of posterior polymorphous corneal dystrophy, have been characterized. PPCD1 mice on the DBA/2J background (D2.Ppcd1) have previously been reported to develop an enlarged anterior chamber due to epithelialization and proliferation of the corneal endothelium and subsequent blockage of the iridocorneal angle. Results presented here show that D2.Ppcd1 mice develop increased intraocular pressure (IOP), with measurements at three months of age revealing significant increases in IOP. Significant retinal ganglion cell layer cell loss is observed at five months of age. D2.Ppcd1 animals also exhibit marked degeneration of the outer nuclear layer in association with hyperplasia of the retinal pigment epithelium. Evidence of retinal detachment is present as early as three weeks of age. By 3.5 months of age, focal areas of outer nuclear layer loss are observed. Although the GpnmbR150X mutation leads to increased IOP and glaucoma in DBA/2J mice, development of anterior segment and retinal defects in D2.Ppcd1 animals does not depend upon presence of the GpnmbR150X mutation.
The Ability of Nitric Oxide to Lower Intraocular Pressure Is Dependent on Guanylyl Cyclase
Invest Ophthalmol Vis Sci. 2017 Sep 1;58(11):4826-4835. doi: 10.1167/iovs.17-22168.
PURPOSE: While nitric oxide (NO) donors are emerging as treatments for glaucoma, the mechanism by which NO lowers intraocular pressure (IOP) is unclear. NO activates the enzyme guanylyl cyclase (GC) to produce cyclic guanosine monophosphate. We studied the ocular effects of inhaled and topically applied NO gas in mice and lambs, respectively.
METHODS: IOP and aqueous humor (AqH) outflow were measured in WT and GC-1α subunit null (GC-1-/-) mice. Mice breathed 40 parts per million (ppm) NO in O2 or control gas (N2/O2). We also studied the effect of ocular NO gas exposure (80, 250, 500, and 1000 ppm) on IOP in anesthetized lambs. NO metabolites were measured in AqH and plasma.
RESULTS: In awake WT mice, breathing NO for 40 minutes lowered IOP from 14.4 ± 1.9 mm Hg to 10.9 ± 1.0 mm Hg (n = 11, P < 0.001). Comparable results were obtained in anesthetized WT mice (n = 10, P < 0.001). In awake or anesthetized GC-1-/- mice, IOP did not change under similar experimental conditions (P ≥ 0.08, n = 20). Breathing NO increased in vivo outflow facility in WT but not GC-1-/- mice (+13.7 ± 14.6% vs. -12.1 ± 9.4%, n = 4 each, P < 0.05). In lambs, ocular exposure to NO lowered IOP in a dose-dependent manner (-0.43 mm Hg/ppm NO; n = 5 with 40 total measurements; P = 0.04) without producing corneal pathology or altering pulmonary and systemic hemodynamics. After ocular NO exposure, NO metabolites were increased in AqH (n = 8, P < 0.001) but not in plasma.
CONCLUSIONS: Breathing NO reduced IOP and increased outflow facility in a GC-dependent manner in mice. Exposure of ovine eyes to NO lowers IOP.
Iridociliary cysts masquerading as neoplasia in cats: a morphologic review of 14 cases
Vet Ophthalmol. 2018 Mar;21(2):125-131. doi: 10.1111/vop.12484. Epub 2017 Jul 6.
OBJECTIVE: To report 14 neoplasia-free feline eyes enucleated for suspected intraocular neoplasia containing only iridociliary cysts. To analyze clinical findings that may have led veterinarians to suspect neoplasia in these globes.
PROCEDURES: The archives at the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) were searched to identify neoplasia-free feline globes enucleated for suspected neoplasia. Clinical data were obtained from medical records, veterinarian surveys, and COPLOW submission forms. All samples were examined grossly and histologically.
RESULTS: All eyes were free of neoplasia and contained one or more iridociliary cysts. Nine of 14 globes were enucleated by or based on the recommendation of a board-certified veterinary ophthalmologist. In eight of 14 cases, the submitting clinician listed melanoma as the only suspected diagnosis; in six of 14 cases, 'tumor' or 'mass' was listed. Clinical examination revealed a darkly pigmented intraocular mass in 11 of 14 cases. The mass was clinically perceived to be within the iris in seven of 14 cases. When examined histologically, 11 of 14 eyes contained multiple cysts, 13 of 14 contained multiloculated cysts, eight of 14 had a hyperplastic iris pigmented epithelium or cysts with thick black walls, and five of 14 had cysts prolapsed into the anterior chamber.
CONCLUSIONS: Although most iridociliary cysts in cats are easily diagnosed on clinical examination, a subset may be mistaken for neoplasia. In cases of suspected iris melanoma, iridociliary cysts should be considered as a differential diagnosis, especially if a mass appears to emanate from behind the iris, dyscoria is present, or if similar changes are noted in the contralateral eye.
Metastatic intraocular hemangiopericytoma in a dog
Open Vet J. 2017;7(2):132-138. doi: 10.4314/ovj.v7i2.9. Epub 2017 May 22.
A 10-year-old Labrador Retriever who had been undergoing therapy for a recurrent hemangiopericytoma of the right flank presented to the Kansas State University Ophthalmology service for evaluation of a painful left eye. Examination revealed secondary glaucoma and irreversible blindness of the affected eye and multifocal chorioretinal lesions in the fellow eye. Therapeutic and diagnostic enucleation of the left eye was performed and histopathologic examination demonstrated the presence of a presumed metastatic spindle cell sarcoma. Further immunohistochemical staining confirmed the intraocular neoplasia to be metastatic spread from the previously removed flank mass. Rapid progression in size and number of chorioretinal lesions in the right eye was noted in the post-operative period until the patient was euthanized one month after surgery. This case report is the first to document intraocular metastasis of hemangiopericytoma in a veterinary patient.
Highly efficient maternal-fetal Zika virus transmission in pregnant rhesus macaques
PLoS Pathog. 2017 May 25;13(5):e1006378. doi: 10.1371/journal.ppat.1006378. eCollection 2017 May.
Infection with Zika virus (ZIKV) is associated with human congenital fetal anomalies. To model fetal outcomes in nonhuman primates, we administered Asian-lineage ZIKV subcutaneously to four pregnant rhesus macaques. While non-pregnant animals in a previous study contemporary with the current report clear viremia within 10-12 days, maternal viremia was prolonged in 3 of 4 pregnancies. Fetal head growth velocity in the last month of gestation determined by ultrasound assessment of head circumference was decreased in comparison with biparietal diameter and femur length within each fetus, both within normal range. ZIKV RNA was detected in tissues from all four fetuses at term cesarean section. In all pregnancies, neutrophilic infiltration was present at the maternal-fetal interface (decidua, placenta, fetal membranes), in various fetal tissues, and in fetal retina, choroid, and optic nerve (first trimester infection only). Consistent vertical transmission in this primate model may provide a platform to assess risk factors and test therapeutic interventions for interruption of fetal infection. The results may also suggest that maternal-fetal ZIKV transmission in human pregnancy may be more frequent than currently appreciated.
Do you see what I see? Optical morphology and visual capability of 'disco' clams (<em>Ctenoides ales</em>)
Biol Open. 2017 May 15;6(5):648-653. doi: 10.1242/bio.024570.
The 'disco' clam Ctenoides ales (Finlay, 1927) is a marine bivalve that has a unique, vivid flashing display that is a result of light scattering by silica nanospheres and rapid mantle movement. The eyes of C. ales were examined to determine their visual capabilities and whether the clams can see the flashing of conspecifics. Similar to the congener C. scaber, C. ales exhibits an off-response (shadow reflex) and an on-response (light reflex). In field observations, a shadow caused a significant increase in flash rate from a mean of 3.9 Hz to 4.7 Hz (P=0.0016). In laboratory trials, a looming stimulus, which increased light intensity, caused a significant increase in flash rate from a median of 1.8 Hz to 2.2 Hz (P=0.0001). Morphological analysis of the eyes of C. ales revealed coarsely-packed photoreceptors lacking sophisticated structure, resulting in visual resolution that is likely too low to detect the flashing of conspecifics. As the eyes of C. ales are incapable of perceiving conspecific flashing, it is likely that their vision is instead used to detect predators.
Orbital rhabdomyosarcoma and traumatic neuroma following enucleation for a uveal schwannoma in a dog: a case report
Clin Case Rep. 2017 Feb 3;5(3):300-307. doi: 10.1002/ccr3.842. eCollection 2017 Mar.
A 4-year-old, female spayed Siberian husky with history of a uveal schwannoma presented for orbital swelling 9 months after enucleation. A second, malignant tumor developed in the same orbit. Therefore, uveal schwannomas may warrant early surgical intervention in the dog.
The consequences of avian ocular trauma: histopathological evidence and implications of acute and chronic disease
Vet Ophthalmol. 2017 Nov;20(6):496-504. doi: 10.1111/vop.12453. Epub 2017 Jan 10.
OBJECTIVE: To present a description and categorization of the histopathological lesions in avian ocular trauma.
ANIMAL STUDIED: Seventy-five birds diagnosed with ocular trauma at to the Comparative Ocular Pathology Laboratory of Wisconsin.
PROCEDURES: Histological slides were reviewed, and the type of trauma was classified by cause into either (i) blunt trauma or (ii) penetrating trauma and by duration into (i) acute or (ii) chronic.
RESULTS: Blunt trauma was the most common source of trauma, and the most frequent lesions were observed in the retina (91%), with 71% of retinas having a tear or detachment and 46% of retinas showing chronic degenerative changes. Damage to the iris/ciliary body was present in 77% of cases. Corneal (17%) and lens (31%) lesions were relatively low. Acute traumatic events had a higher prevalence of readily identifiable discrete retinal tears/detachments (64%). Nearly all cases of chronic trauma exhibited chronic retinal lesions (93.7%), as well as a greater percentage of cartilage/bone lesions (71.4%), irido/cyclodialysis (51.9%), lenticular lesions (72.7%), and corneal damage (83.3%). However, the incidence of iridocyclodialysis was roughly equivalent for acute and chronic blunt trauma.
CONCLUSIONS: Ocular trauma can lead to profound acute and chronic lesions within the eye. Here, we provide insight into understanding ocular damage caused by trauma, which may help future studies suggest new therapeutic options and provide insight regarding the releasability of avian wildlife.
Uveal schwannoma in a brown-eyed dog
Vet Ophthalmol. 2018 Mar;21(2):205-209. doi: 10.1111/vop.12458. Epub 2017 Jan 17.
An eleven-year-old, female spayed Boxer dog was diagnosed with a uveal schwannoma (formerly known as the spindle cell tumor of the blue-eyed dog or SCTBED) despite having a uniformly brown iris. The patient presented to emergency for ocular discomfort, and the right globe was subsequently enucleated due to glaucoma and submitted for histopathology. Upon histopathologic evaluation, a uveal schwannoma was diagnosed and confirmed with immunohistochemical staining. Complete metastatic evaluation 1 and 6 months after initial presentation did not reveal evidence of metastasis, and the dog remains systemically healthy. This case represents a unique variant of uveal schwannoma and is relevant because although the vast majority of these tumors occur in blue-eyed dogs, clinicians should not completely rule out this tumor as a differential based on the iris color.
A Mouse Model of Multi-Drug Resistant <em>Staphylococcus aureus</em>-induced Ocular Disease
J Ocul Biol. 2016 Nov;4(2):10.13188/2334-2838.1000026. doi: 10.13188/2334-2838.1000026. Epub 2016 Nov 10.
Staphylococcus aureus infection of the cornea is a significant threat to vision. The percentage of bacterial isolates resistant to antibiotics is increasing as is the percentage of infections caused by methicillin resistant isolates. There is a critical need for additional therapeutic approaches and their development will require the use of animal models to test efficacy. Two mouse models of S. aureus keratitis have been described but only quantified stromal keratitis (corneal clouding and perforation). We have extended these models using the methicillin resistant S. aureus USA300 LAC strain and show that eyelid inflammation and swelling (blepharitis) and corneal neovascularization can be quantified. This expanded model should prove useful in assessing additional effects of antibacterial therapies and additional pathological mechanisms involved in bacterial ocular infection.
Modeling the Chronic Loss of Optic Nerve Axons and the Effects on the Retinal Nerve Fiber Layer Structure in Primary Disorder of Myelin
Invest Ophthalmol Vis Sci. 2016 Sep 1;57(11):4859-4868. doi: 10.1167/iovs.16-19871.
PURPOSE: We determined whether the chronic lack of optic nerve myelination and subsequent axon loss is associated with optical coherence tomography (OCT) changes in the retinal nerve fiber layer (RNFL), and whether this models what occurs in multiple sclerosis (MS) and confers its use as a surrogate marker for axon degeneration.
METHODS: Using an animal model of Pelizaeus-Merzbacher disease (shp) bilateral longitudinal measurements of the peripapillary RNFL (spectral-domain OCT), electroretinograms (ERG), and visual evoked potentials (VEP) were performed in affected and control animals from 5 months to 2 years and in individual animals at single time points. Light and electron microscopy of the optic nerve and retina and histomorphometric measurements of the RNFL were compared to OCT data.
RESULTS: Of the shp animals, 17% had an average reduction of OCT RNFL thickness on the superior retinal quadrant compared to controls (P < 0.05). Electroretinograms showed normal photopic A- and B-waves but flash VEPs were disorganized in shp animals. Morphologically, the shp retinas and optic nerves revealed significant RNFL thinning (P < 0.001) without retinal ganglion cell (RGC) loss, decrease total and relative retinal axonal area, and loss of optic nerve axons. There was strong positive correlation between OCT and morphometric RNFL thickness measurements (r = 0.878, P = 0.004).
CONCLUSION: The loss of optic nerve axons demonstrated in the shp model resulted in moderate thinning of the RNFL confirmed by OCT and histology. These results indicate that OCT-derived RNFL measurement can be a useful surrogate biomarker of optic nerve axon loss and potentially disease progression in demyelinating diseases.
Association of a Chromosomal Rearrangement Event with Mouse Posterior Polymorphous Corneal Dystrophy and Alterations in Csrp2bp, Dzank1, and Ovol2 Gene Expression
PLoS One. 2016 Jun 16;11(6):e0157577. doi: 10.1371/journal.pone.0157577. eCollection 2016.
We have previously described a mouse model of human posterior polymorphous corneal dystrophy (PPCD) and localized the causative mutation to a 6.2 Mbp region of chromosome 2, termed Ppcd1. We now show that the gene rearrangement linked to mouse Ppcd1 is a 3.9 Mbp chromosomal inversion flanked by 81 Kbp and 542 bp deletions. This recombination event leads to deletion of Csrp2bp Exons 8 through 11, Dzank1 Exons 20 and 21, and the pseudogene Znf133. In addition, we identified translocation of novel downstream sequences to positions adjacent to Csrp2bp Exon 7 and Dzank1 Exon 20. Twelve novel fusion transcripts involving Csrp2bp or Dzank1 linked to downstream sequences have been identified. Eight are expressed at detectable levels in PPCD1 but not wildtype eyes. Upregulation of two Csrp2bp fusion transcripts, as well as upregulation of the adjacent gene, Ovol2, was observed. Absence of the PPCD1 phenotype in animals haploinsufficient for Csrp2bp or both Csrp2bp and Dzank1 rules out haploinsufficiency of these genes as a cause of mouse PPCD1. Complementation experiments confirm that PPCD1 embryonic lethality is due to disruption of Csrp2bp expression. The ocular expression pattern of Csrp2bp is consistent with a role for this protein in corneal development and pathogenesis of PPCD1.
Proceedings of the 2015 National Toxicology Program Satellite Symposium
Toxicol Pathol. 2016 Jun;44(4):502-35. doi: 10.1177/0192623316631844. Epub 2016 Apr 12.
The 2015 Annual National Toxicology Program Satellite Symposium, entitled "Pathology Potpourri" was held in Minneapolis, Minnesota, at the American College of Veterinary Pathologists/American Society for Veterinary Clinical Pathology/Society of Toxicologic Pathology combined meeting. The goal of this symposium is to present and discuss diagnostic pathology challenges or nomenclature issues. Because of the combined meeting, both laboratory and domestic animal cases were presented. This article presents summaries of the speakers' talks, including challenging diagnostic cases or nomenclature issues that were presented, along with select images that were used for audience voting and discussion. Some lesions and topics covered during the symposium included hepatocellular lesions, a proposed harmonized diagnostic approach to rat cardiomyopathy, crop milk in a bird, avian feeding accoutrement, heat exchanger in a tuna, metastasis of a tobacco carcinogen-induced pulmonary carcinoma, neurocytoma in a rat, pituicytoma in a rat, rodent mammary gland whole mounts, dog and rat alveolar macrophage ultrastructure, dog and rat pulmonary phospholipidosis, alveolar macrophage aggregation in a dog, degenerating yeast in a cat liver aspirate, myeloid leukemia in lymph node aspirates from a dog, Trypanosoma cruzi in a dog, solanum toxicity in a cow, bovine astrovirus, malignant microglial tumor, and nomenclature challenges from the Special Senses International Harmonization of Nomenclature and Diagnostic Criteria Organ Working Group.