Unilateral ocular subalbinism in a laboratory Beagle dog

Blue discoloration of the iris was found in the left eye of a male laboratory Beagle dog, which had a normal tricolor coat and clinically showed no visual impairment. Ophthalmoscopically, the affected eye revealed red-colored tigroid fundus, in which no tapetum was present. The retinal vasculature and the optic disc showed no noticeable changes. Histopathologically, in the left eye melanocytes had extremely few melanin granules in the anterior segment, including the anterior border layer, in the stroma and sphincter muscle of the iris and in the stroma of the ciliary body and choroid. However, the posterior pigment epithelium of the iris, the pigment epithelium of the ciliary body and the retinal pigment epithelium showed normal pigmentation. The tapetal elements were completely absent. Number and distribution of the S-100 protein-positive melanocytes with or without melanin granules in the iris, ciliary body and choroid of the left eye were similar to those of the normal right eye. Ultrastructurally, melanocytes in the anterior segment of the affected iris possessed no or few melanosomes which were incompletely melanized. In the right eye, no abnormal features were observed. Based on these results, the present case was diagnosed as unilateral ocular subalbinism with tapetal aplasia in a Beagle dog.     

Malignant melanoma in a zebra finch (Taeniopygia guttata): cytologic, histologic, and ultrastructural characteristics

An approximately 3-year-old adult male zebra finch (Taeniopygia guttata) was diagnosed with malignant melanoma. The large darkly pigmented tumor was located in the coelom, extended from the apex of the heart to the cloaca, and was adherent to the intestines and the ventriculus. Dark small masses (likely metastases) were observed in the lungs. Cytologically, the neoplasm consisted mainly of round to oval cells with brown or pale blue to blue-brown pigment. Lesser numbers of cells were stellate to dendritic with abundant amounts of brown pigment granules or were markedly pleomorphic with variable amounts of pigment. Histologically, the tumor consisted of dense sheets and aggregates of infiltrative melanocytes that were negative for S-100 and Melan A. A few cells were consistent with "signet-ring" melanocytes. Melanocytes examined by electron microscopy contained typical structures, mainly premelanosomes and melanosomes, of this cell type. However, melanocytes with marked pleomorphism also contained intracytoplasmic aggregates of filaments, consistent with previously reported ultrastructural findings in signet-ring or rhabdoid melanoma of nonavian species.     

Intercellular junctions in rabbit eye ora serrata

Summary The aim of this study was to describe and localize the intercellular junctions in the ora serrata region of albino and pigmented rabbit eyes. Eyes of albino and pigmented rabbits were fixed and processed for transmission electron microscopy. Light and electron microscope examination was carried out on semithin and ultrathin sections. The ora serrata region showed adherens, gap and tight junctions in the retinal and ciliary margins of albino and pigmented rabbit eyes. In the retinal margin, zonulae adherens between Müller cells and photoreceptors are associated with tight junctions. In the ciliary margin, epithelial cells are joined by adherens, gap and tight junctions localized between apical and apicolateral cell membranes. Tight junctions appear as zonulae occludens in the non-pigmented apicolateral cell membranes and as tight focal junctions between pigmented and non-pigmented apical cell membranes. Between the ciliary and retinal margins there are adherens and tight focal junctions which attach pigmented apical cell membranes to adjacent cells. There were no differences in the distribution of intercellular junctions between albino and pigmented rabbits.     

Ocular manifestations of equine motor neuron disease

The characteristics of the ocular manifestations of equine motor neuron disease (EMND) are described. Forty-two horses with histories, clinical signs and necropsies compatible with EMND were the subjects of this study. Ophthalmoscopic lesions that varied in severity were found in 40 of 42 horses and appeared as a distinct pigmented reticulated pattern at the tapetal-nontapetal junction or throughout the fundus, depending upon severity. The pattern colours ranged from yellow brown to black. Areas of hyperreflectivity formed mosaic patterns in the tapetal fundus. ERG B-wave amplitudes were usually at least 50% reduced and many animals showed extinguished amplitudes. None of the horses had apparent visual impairment. Histopathologically, all 42 horses had retinal pigment epithelial (RPE) congestion with ceroid-lipofuscin. Retinal degeneration was variable even within the eyes. Thin layer chromatography (TLC) analysis of the RPE and neural retina identified both green and orange emitting fluorescent compounds not found in normal horses. All unsupplemented horses had plasma vitamin E levels <1.0 microg/ml. The potential significance of this report is the pathognomonic role the ocular manifestations exhibit in helping to diagnose equine motor neuron disease.     

Black hair follicular dysplasia in Large Münsterländer dogs: clinical, histological and ultrastructural features

Four Large Münsterländer cross‐bred dogs affected with black hair follicular dysplasia (BHFD) and one unaffected control littermate were observed, and skin was sampled weekly over the first 19 weeks of life. Affected dogs were born with silvery grey hair, a consequence of melanin clumping in the hair shafts. Hair bulb melanocytes were densely pigmented, and contained abundant stage IV melanosomes but adjacent matrix keratinocytes lacked melanosomes. Melanin clumping was not prominent in epidermal melanocytes in the haired skin but occurred in the foot pads. Follicular changes progressed from bulbar clumping, clumping in the isthmus/infundibulum and finally to dysplastic hair shafts. Alopecia developed progressively in pigmented areas. Silver‐grey hair, melanin clumping, accumulation of stage IV melanosomes within melanocytes and insufficient melanin transfer to adjacent keratinocytes are also classic features of human Griscelli syndrome. The underlying cause in Griscelli syndrome is a defect of melanocytic intracellular transport proteins leading to inadequate and disorganized melanosome transfer to keratinocytes with resultant melanin clumping. In view of the correlation in the phenotype, histology and ultrastructure between both disorders, a defect in intracellular melanosome transport is postulated as the pathogenic mechanism in BHFD.     

The influence of aging and low zinc nutrition on the choroid in the pig: II. The melanosome

The effects of low zinc nutrition and aging on central choroidal melanosomes were examined in the pig. Melanosomes of central choroidal melanocytes were morphologically and morphometrically examined in three populations of pigs (young, pregnant and aged), that were maintained on either control (C) or low zinc (LZ) diets. In C groups, the typical melanosomes decreased in size with age, although a subpopulation of larger melanosomes occurred in the oldest group. In contrast, the melanosomes of the animals on LZ diets increased in size significantly in the adult groups. The melanosomes in the pregnant and aged groups were 65% and 30–40% greater than those of the age-matched C groups. Extremely large melanosomes were frequently encountered in adult LZ choroidal melanocytes. Melanogenesis of these large bodies included the formation of one or more outer shells. Fusion of adjacent large melanosomes was also observed. Melanolysosomal-like bodies were observed, particularly among the pigmented cells in the large blood vessel region of C and LZ adults. Melanin dynamics, i.e. its production and breakdown, occurred within choroidal melanocytes throughout much of the lifespan of the pig. This dynamic was greatly influenced by low zinc nutrition, resulting in unusual and aberrant melanin activity.     

Abnormal ocular pigment deposition and glaucoma in the dog

The combined occurrence of ocular pigment deposition and glaucoma has been described in Cairn Terriers. Recently, this condition was also observed in two other breeds: the Boxer (two cases) and the Labrador Retriever (one case). Six dogs were referred to the Ophthalmology section of the Department of Clinical Sciences of Companion Animals and to a private referral clinic because of glaucoma or blindness in one or both eyes. In five cases ophthalmic examination showed pigment depositions in the sclera around the entire circumference of the perilimbal zone. Eight enucleated eyes (four eyes of two Cairn Terriers, three eyes of two Boxers and one eye of a Labrador Retriever) were examined microscopically. All eyes showed the same findings: an extensive infiltration of large melanin-containing cells with an eccentric nucleus, located in the iris, ciliary body, retina, choroids and sclera. Transmission electron microscopy of two of the examined eyes revealed that the morphology of most of these cells was consistent with melanophages. While reports in the veterinary literature concerning this condition are limited the cells concerned have been described to be melanocytes. Further research is needed to conclusively identify the cell type. As described in the present report, the histologic and transmission electron microscopic findings suggest a different etiology of the ocular pigment deposition and glaucoma compared with the pigment dispersal syndrome in humans.     

Congenital ocular abnormalities of Rocky Mountain Horses

Objective: To determine the incidence and describe ocular abnormalities in a cross-section of the population of Rocky Mountain Horses.
Design: Prospective study.
Animals: Five-hundred and fourteen Rocky Mountain Horses.
Procedure: Ophthalmic examinations were performed using a slit-lamp biomicroscope and an indirect ophthalmoscope. Intraocular pressures were measured by applanation tonometry. Eyes from six horses were obtained for histologic examination.
Results: Cysts of the posterior iris, ciliary body, and peripheral retina were detected most frequently (249 horses), and were always located temporally. Curvilinear streaks of retinal pigmented epithelium extending from the peripheral temporal retina marked the boundary of previous retinal detachment in 189 horses. Retinal dysplasia was detected in 125 horses. Multiple ocular anomalies were evident in 71 horses and were always bilateral and symmetrical. Affected eyes had a large, clear cornea that protruded excessively and had an apparent short radius of curvature, a deep anterior chamber, miotic and dyscoric pupil, and iris hypoplasia. Pupillary light responses were decreased or absent and pupils failed to dilate after repeated instillation of mydriatic drugs in horses with multiple ocular anomalies. Less frequently encountered abnormalities included peripheral iridocorneal adhesions and goniosynechiae. Congenital cataract was always present in eyes with multiple abnormalities. Intraocular pressures did not differ among horses with normal eyes and horses with multiple ocular abnormalities. Histologic examination of eyes corroborated the clinical appearance.     

SLC24A5基因影响脊椎动物色素沉积的研究进展

黑色素广泛分布于细菌、真菌、植物和动物体内并扮演了重要的作用。人类浅色皮肤的色素沉积是由于黑色素细胞内黑色素小体数量、大小和密度的减少造成的,而黑色素小体变化也导致斑马鱼由灰色突变为金色,这个金色突变位点编码一个推定的阳离子交换体SLC24A5基因,该基因位于黑色素小体或其前体的细胞膜上。人类和斑马鱼在这个基因的序列及功能上有很高的同源性。该基因的多态性主要出现在非洲和东亚人身上。而等位基因固定在欧洲人的身上,这与局部杂和性大量减少和较浅的皮肤色素沉积有关,表明SLC24A5基因在人类色素沉积方面起关键作用。作者总结了SLC24A5基因与黑色素的研究进展,并简要介绍了乌骨绵羊的发现及其分子特征。     

Congenital ocular anomalies in purebred and crossbred Rocky and Kentucky Mountain horses in Canada

Multiple congenital ocular anomalies in purebred and crossbred Rocky and Kentucky Mountain horses in Canada are frequently diagnosed with biomicroscopic and indirect ophthalmoscopic examination. In order of frequency detected, these include temporal ciliary epithelial cysts; iridal hypoplasia; prominent corneas; focal temporal retinal degeneration related to ciliary cysts; and, rarely, retinal detachment. A pedigree analysis confirms a dominant mode of inheritance with incomplete penetrance and with a linkage to coat color.     

The pathogenesis and significance of pre-iridal fibrovascular membrane in domestic animals

Histologic examination was made of 1,419 globes from domestic animals (964 dogs, 374 cats, 41 horses, and 40 cattle) with ocular disease; pre-iridal membranes (rubeosis iridis) were found in 98. The membranes originated as endothelial budding from the anterior iridal stroma and seemed to mature into fibrous or fibrovascular membranes that were often followed by hyphema or, occasionally, glaucoma. Pre-existent disease in the 98 affected globes included chronic endophthalmitis (27/98), chronic glaucoma (24/98), anterior uveal melanoma (15/98), ciliary body adenoma (14/98), neoplasms metastatic to the eye (8/98), and chronic retinal detachment (6/98). In terms of likelihood of occurrence, pre-iridal membranes seen in 21% (6/21) of globes with retinal detachment, 19% (14/75) of those with ciliary body adenomas, 14% (24/167) of those with chronic glaucoma, and 10% (15/158) of those with anterior uveal melanoma. They were detected with greatest relative frequency in horses (9/41) followed by dogs (83/964), cats (5/374) and cattle (1/40). These membranes, which are rarely detected by clinical examination, probably form in response to angiogenic factors released by ischemic retina, by neoplasms, or by leukocytes involved in ocular inflammation.     

Melanocytogenesis and melanogenesis: genetic regulation and comparative clinical diseases

Murine models recently provided important information on the pathogenesis of pigmentation disorders. Multiple factors influence melanocyte function at various levels, such as melanoblast development and migration from the neural crest to peripheral sites, melanoblast differentiation into melanocytes, melanocyte survival and, finally, synthesis of melanosomes and melanins. Mutations affecting any of these steps result in hereditary hypomelanoses. In some of these diseases, melanocytes are absent, either because of a defect in migration of melanoblasts from the neural crest, their inability to survive and/or proliferate in colonized territories (piebaldism and Waardenburg syndromes), or because of programmed melanocyte destruction (e.g. vitiligo). In other entities, the melanocytes are present but functionally deficient (oculocutaneous albinisms and pigmentary dilutions). This comprehensive review will introduce the genetic regulation of melanocytogenesis and melanogenesis and the correlations between genetic abnormalities and hypopigmentation clinical disorders.     

Multifocal chorioretinal lesions in Borzoi dogs

OBJECTIVES: To identify the prevalence of Borzoi chorioretinopathy in western Canada, characterize lesions with fluorescein angiography, determine if lesions were progressive, clarify the association of progressive retinal atrophy and investigate the etiology. MATERIALS AND METHODS: Serial ophthalmic examination, fundus photography, electroretinography, and fluorescein angiography were used to evaluate Borzoi dogs with lesions of Borzoi chorioretinopathy. Pedigree analysis and test breeding of two affected dogs were completed to determine the heritability of Borzoi chorioretinopathy. RESULTS: One hundred three Borzoi dogs were examined between 1998 and 2003. Focal, peripheral, tapetal, hyper-reflective and pigmented areas consistent with focal retinal degeneration and RPE pigmentation were identified in 12 dogs between 7 months and 7 years of age. Seven males and five female dogs were affected. Ophthalmoscopy and fundus photography over 5 years revealed individual lesions that did not progress or coalesce in 12 affected dogs. Electroretinography of affected and normal Borzoi dogs confirmed that retinal function was similar in normal and affected dogs up to 7 years of age. Fluorescein angiography was performed in three affected dogs and confirmed intact blood-ocular barriers, focal retinal pigment epithelium hypertrophy, and focal absence of choroiocapillaris corresponding to chronic, focal lesions. Pedigree analysis precluded simple dominant, X-linked dominant, or X-linked recessive inheritance. One male dog from the test-bred litter developed bilateral lesions at 14 months of age. Simple recessive, polygenetic, and acquired etiologies of these lesions cannot be ruled out at this time. CONCLUSIONS: Borzoi chorioretinopathy is an acquired condition that initially manifests as focal retinal edema and loss of choriocapillaris and tapetum. With time the retina degenerates becoming hyper-reflective and with RPE hyper-pigmentation and clumping within the borders of the tapetal lesions. Choriocapillaris remains hypofluorescent on fluorescein angiography. Progressive retinal atrophy was excluded as an etiology of multifocal chorioretinopathy in Borzois dogs. This condition is not inherited by simple autosomal dominant or sex-linked modes of inheritance.     

Ocular melanosis in the Cairn Terrier: histopathological description of the condition, and immunohistological and ultrastructural characterization of the characteristic pigment-laden cells

Objective  To describe the microscopic features and lineage of proliferating/infiltrating pigmented cells in ocular melanosis of Cairn Terriers.
Animals studied  Forty-nine globes removed from 45 Cairn Terriers with ocular melanosis and three globes from control dogs were available for microscopic examination.
Procedures  All globes were examined histologically, eight affected and three control globes were also examined by immunohistochemistry, and three affected and three control globes by transmission electron microscopy.
Results  Large round pigment-laden cells infiltrated the anterior uvea, obscured the drainage angle and were present within the sclera and episclera of affected globes. Similar pigmented cells were present in lower numbers in the posterior segment of the globe, the optic nerve meninges and periphery of the optic nerve. Changes due to chronic glaucoma were present in many globes and some had evidence of uveitis. Many of the pigmented cells were immunoreactive to HMB45 and some were MITF and vimentin positive. One globe, which was inflamed when removed, had many pigmented cells that were CD18 immunoreactive. The other eyes had lower numbers of CD18 positive cells. The pigmented cells were not immunoreactive to smooth muscle actin, S-100, MART/Melan A, chromogranin A/B, PGP 9.5, synaptophysin, MNF116, AE1/AE3, and CD45. Ultrastructurally many of the pigmented cells had features typical of melanocytes while a smaller number appeared to be melanophages.
Conclusions  Ocular melanosis in Cairn Terriers is characterized by an infiltration of pigment-laden cells predominantly, but not exclusively, within the anterior uvea and anterior sclera. Most of these cells appear to be melanocytes although a variable proportion are pigment-laden melanophages.     

A portable, contact animal fundus imaging system based on Rol's GRIN lenses

Objective To demonstrate a cost‐effective, portable, and simple‐to‐use fundus imaging system for laboratory animals. Animals Studied Albino rats, pigmented mice, albino guinea pigs, and New Zealand white rabbits. Procedure A contact fundus imaging system was designed and constructed using standard optical and mechanical components: a digital camera, an otoscope, a fiber optic light source, and standard optical lenses and mounts. Digital fundus video and photography of two albino rats, two pigmented mice, two New Zealand white rabbits, and two albino guinea pigs were obtained. For all animals examined, pupils were dilated and local anesthetic was administered. Results Digital images of the fundus were obtained in all animals. Contrast of retinal vasculature and overall image quality varied from one species to another, as the axial length, ocular optics, and retinal reflectance varied significantly across species. Light intensity and focus were optimized via the light source and lens focusing mount to produce high‐quality images for each animal. Conclusions The portable, cost‐effective contact fundus imaging system was easy to use for fundus examination of laboratory animals.     

Cutaneous melanophoroma in a green iguana (Iguana iguana)

An adult, male, green iguana (Iguana iguana) of unknown age was presented with a history of an enlarging, dark, skin mass in the right axillary region. The mass was excised because neoplasia was suspected. Impression smears of the cut surface of the mass were prepared for cytologic examination, and the mass was fixed for histologic examination. The impression smears contained numerous, discrete, pigmented, neoplastic cells consistent with melanin-producing neoplastic chromatophores. Histologic findings were consistent with a cutaneous melanophoroma. By transmission electron microscopy, the intracytoplasmic pigment granules corresponded to numerous melanosomes and lower numbers of premelanosomes. Tissue sections of the tumor were immunoreactive for Melan A antigen and were negative for S-100 antigen. The cytologic, histologic, electron microscopic, and immunohistochemical findings of the neoplasm were consistent with those of melanophoroma, an uncommon neoplasm of reptiles. The present report augments the limited body of knowledge on cytomorphologic and immunohistochemical characteristics of pigmented neoplasms in reptiles.     

Transpupillary diode laser retinopexy in dogs: ophthalmoscopic,fluorescein angiographic and histopathologic study

Objective To evaluate the ophthalmoscopic, fluorescein angiographic and light microscopic effects of diode laser retinopexy application in the tapetal and nontapetal fundus in the dog, and to ascertain appropriate laser power settings for production of photocoagulative lesions in these two regions. Animals studied Three adult female Beagle dogs. Procedures Laser burns were applied to selected areas in the fundus with an indirect headset delivery system using settings varying from 100 to 200 milliWatts (mW) and from 100 to 600 milliSeconds (mS) with total delivered energy ranging between 15 and 100 milliJoules (mJ). The dogs were then monitored by ophthalmoscopic examination and fluorescein angiography at regular intervals for 7–28 days. Histopathologic studies were performed at 7, 14 and 28 days after laser application. Results The diode laser produced ophthalmoscopically visible lesions in the nontapetal fundus with all laser settings used, and the appearance of these lesions corresponded to the energy levels used, and degree of pigment in the lased region. Gray‐white colored lesions with minimal subsensory retinal edema were seen with settings as low as 100 mWatts/150 mSeconds. In the tapetal fundus, laser burns were more difficult to produce, less repeatable, and required higher energy levels. Laser burns appeared as bronze, dark green or black discolorations of the tapetum with varying degrees of subsensory retinal edema. Lesions were more reproducible and were achieved with lower settings in the tapetal area of the tapetal/nontapetal junction. Ophthalmoscopically, depigmentation and repigmentation of the RPE (nontapetal fundus) and degenerative changes in the overlying retina (tapetal fundus) developed in the laser burns over the 28‐day study period. Fluorescein angiographic studies showed disruption of the blood–retinal barrier at the level of the RPE and fluorescein leakage into the subsensory retinal space was seen in most lesions at 24 h, was minimal at 3 days, and had resolved by 7 days. Histologically, grayish‐white lesions in the nontapetal fundus, and bronze to small black lesions in the tapetal fundus were typically characterized by outer retinal necrosis and RPE migration. Gliosis was considered minimal, was confined to the retina, and no inflammatory cells were seen. Peripheral intense white lesions (nontapetum) and lesions with a black center (tapetal fundus) were characterized by more extensive panretinal and choroidal necrosis. Most of the nontapetal lesions and a few in the tapetal fundus showed the formation of a central retinal detachment. Conclusions The diode laser effectively produces lesions suitable for retinopexy in both the nontapetal, pigmented fundus and the tapetal fundus, although variably so in the latter region. Initial laser settings of 100–150 mW/200 mS for the pigmented fundus, and 150 mW/200–300 mS for the peripheral tapetal fundus are recommended, and the clinician should gradually increase time interval settings to achieve a grayish‐white lesion in the nontapetum, and a bronze to slightly black lesion in the tapetal fundus. If possible, retinopexy should be applied to the peripheral tapetal area or tapetal/nontapetal junction.     

Ocular lesions of bovine malignant catarrhal fever

The ocular lesions of bovine malignant catarrhal fever were characterized in 15 naturally occurring and eight experimentally induced cases of the disease. Consistent findings included: lymphocytic vasculitis of retinal, scleral, posterior ciliary, and uveal vessels; uveitis, especially involving ciliary processes, ciliary body, and iris; and keratitis with corneal edema, neovascularization, and epithelial and endothelial degeneration. Lymphocytic ciliary neuritis and optic meningitis were found less frequently. Ultrastructural examination of the ciliary body and iris from one experimental calf confirmed that most infiltrating mononuclear cells were lymphocytes. The uveitis, vasculitis, and keratitis of malignant catarrhal fever were probably immune-mediated.     

Drusen and lipid-filled retinal pigment epithelium cells in a rhesus macula

A middle-aged rhesus monkey with detailed clinical history exhibited progression of a macular abnormality with a variety of clinical drusen and pigment changes typical of the Cayo Santiago phenotype. Numerous frozen sections of one sample of the macular retina/retinal pigment epithelium (RPE)/choroid showed a single classical druse but extensive single and clustered lipid-filled RPE cells. The monkey exhibited functional outer retinal decline and an insignificant number of 'window defects' as found among signs of relatively benign human macular aging. The clinical and histologically defined results agree if lipid-filled RPE cells are included among the clinically apparent signs of drusen.