Examination of the rat eye at the early stage of development with osmium tetroxide staining

This communication describes the benefit of osmium tetroxide (OsO4) staining on the examination of the eye during the early stage of organogenesis of rat embryos. The embryos were obtained by laparotomy on embryonic day 12 (ED 12) and were stained with OsO4 for examination of the ocular tissues with a binocular stereo-microscope, light microscope and scanning electron microscope. At the binocular stereo-microscopic level, the invaginated lens placode, lens pit and optic cup were clearly distinguished. The osmium-stained lens placode and the optic cup were light brown and dark brown in color, respectively. Light microscopic examination revealed that OsO4 postfixation could provide superior paraffin-embedded embryonic sections. Scanning electron microscopic examination revealed the lens pit as a round opening between the lateral nasal prominence and maxillary prominence. Thus, a rapid technique by which the ocular tissues of rat embryos can be examined under a binocular stereo-microscope was developed. This OsO4 staining method will provide a useful tool for research on organogenesis and ocular development.     

Quantitative study of the optic nerve in buffaloes (Bos bubalis)

The total number, distribution and size of the optic axons of the buffalo (Bos bubalis) were studied in five optic nerves using light and transmission electron microscopes. Semithin sections were cut at 0.40 μm with an ultramicrotome and stained with 0.3% toluidine blue for light microscopic analysis. The ultrathin sections were cut at 70 nm, mounted on copper mesh grids (No. 200) and stained with saturated solution of uranyl acetate dihydrate and examined with the transmission electron microscope. The optic axons were assessed in 10 regions of roughly equal area. The total number of optic fibers was estimated on semithin and ultrathin sections. The measurements of the axonal diameters were made on electron micrographs taken from various regions across the optic nerve. The mean value of the total number of optic axons calculated was 1 397 099 ± 10 995 and 1 584 255 by light and electron microscopes, respectively. There was very little difference in the density of the optic fibers between the 10 regions of the optic nerve. The optic nerve area ranged from 18.2 to 22.4 mm² (mean, 21.3 mm²). The diameters of the optic axons ranged from 0.5 to 12.3 μm (mean, 3.3 μm).     

First spike latency of ON/OFF neurons in the optic tectum of pigeons

Some shallow and middle optic tectum (OT) neurons have stable, asymmetric full‐screen ON and OFF stimulus response properties, which makes them candidates for delay encoding. In this paper, we investigated the delay encoding mechanism for the neuronal clusters in the OT region of pigeons and determined the mechanism of delay coding in the OT region. By analyzing the responses of the neuron cluster under full‐screen switch‐on and switch‐off stimulation, we found that the delay coding was widespread in the OT region where the ON/OFF stimulation time difference was 4–6 ms. Information theory analysis under grating stimulation and experiments based on single‐neuron character reconstruction of neurons showed that OT neuron clusters use the first spike latency (FSL) for the rapid transfer of spatial structure information. Furthermore, 4 models were used to predict the first spike latency of these OT neurons. The best simulation results were obtained using an architecture where the ON and OFF paths of multiple retinal ganglion cells (RGCs) were integrated and summed, respectively.     

Bilateral neuroepithelial choristomas of the optic disc in a cynomolgus monkey (Macaca fascicularis): a case report

A 6-year-old intact male cynomolgus monkey of Chinese origin was received at the Sierra Biomedical Facility. While physical examination revealed good body condition with no abnormalities, routine ophthalmic examination revealed bilateral proliferative optic neuropathy involving the dorsal aspect of the optic disc. No changes were noted in the appearance of the lesions over 8 months, and fluoroescein angiography revealed no abnormalities other than obstruction of the view of the retinal vessels by the lesions. Histopathologic studies revealed characteristics consistent with a diagnosis of bilateral neuroepithelial choristoma.     

Cytologic appearance of retinal cells included in a fine‐needle aspirate of a meningioma around the optic nerve of a dog

A 6‐year‐old Wirehair Dachshund had a meningioma around the optic nerve that caused exophthalmos. A benign mesenchymal tumor was suspected based on the cytologic pattern of a fine‐needle aspirate, and a meningioma was diagnosed by histopathologic examination. In addition to the meningioma cells, the cytologic smears included groups of cells from apparently 4 layers of normal retina. In particular, uniform rod‐shaped structures in the cytologic sample could suggest rod‐shaped bacteria, but these structures were identified as cylindrical outer segments of photoreceptor rod cells. Other retinal structures recognized included pigmented epithelial layer cells with their uniquely formed pigment granules, the characteristic bi‐lobed, cleaved nuclei from the outer nuclear layer, and nerve tissue likely from the outer plexiform layer of the retina.     

Rapid diagnosis of retina and optic nerve abnormalities in canine patients with and without cataracts using chromatic pupil light reflex testing

Objective To develop fast and reliable testing routines for diagnosing retina and optic nerve diseases in canine cataract patients based on chromatic properties of the pupillary light reflex response. Procedures Seventy‐seven canine patients with a history of cataract and decreased vision (43 patients with cataracts and no evidence of retina or optic nerve disease, 21 patients with cataracts and retinal degeneration [RD], 13 patients with cataracts and retinal detachment [RDT]), 11 canine patients with optic neuritis (ON) and 23 healthy dogs were examined using chromatic pupillary light reflex (cPLR) analysis with red and blue light and electroretinography. Results Electroretinography analysis showed statistically significant deficits in a‐ and b‐wave amplitudes in dogs with cataracts and RD, or cataracts and RDT, when compared to dogs with cataracts without evidence of retinal abnormalities. Evaluation of b‐wave amplitudes showed that presence of 78.5‐μV (or lower) amplitudes had high sensitivity of 100% (95% CI: 87.2–100%) and high specificity of 96.7% (95% CI: 88.4–100%) in RD and RDT. Evaluation of cPLR responses using red light showed that presence of the pupil end constriction diameter of 5.5 mm (or higher) had moderately high sensitivity of 76.5% (95% CI: 50.1–93.2%) and high specificity of 100% (95% CI: 91.2–100%) in detecting RD and RDT. Optic neuritis patients had absent cPLR responses, regardless of the visual status. Conclusions and Clinical Relevance Chromatic evaluation of the pupillary light reflex is a rapid and accurate test for diagnosing retina and optic nerve diseases in canine patients.     

Expression of glial cells molecules in the optic nerve of adult dromedary camel (Camelus dromedarius): A histological and immunohistochemical analysis

The optic nerve (ON) is an important organ in the visual system of animals, which transfers electrical impulses towards the brain from the retina. High enrichment of glial cells in ON is known to support neuron and regulate retinal homoeostasis. However, research on immunohistochemical of glial cells proteins in the camel is scanty in available literature. Hence, the current work is an attempt to investigate the histomorphology of camel ON with regard to the expression patterns of glial fibrillary acidic protein (GFAP), myelin basic protein (MBP) and Iba1 for the three glial subtypes, namely astrocytes, oligodendrocytes and microglia, respectively. Optic nerves from fourteen dromedary camels were dissected and preserved in 10% formalin. Then, the paraffin‐embedding sections were subjected for histochemical and immunohistochemical analysis. Our results demonstrated that ON axons aggregate into fascicles that surrounded by light and densely stained glial cells. Then, we examined the myelin sheath using Heidenhain's and Mallory's phosphotungstic acid staining. Immunoassay results revealed that GFAP is enriched in the ON and distributed evenly, whereas MBP and Iba1 were present at scanty levels. Further analysis of mRNA level of GFAP, MBP and Iba1 in the ON confirmed an elevation of GFAP expression compared to MBP and Iba1. We further found partial co‐localization of different types of glial cells that reflect their coordinated function in the ON. Although our data provide the first evidence for differential expression pattern of glial proteins, further molecular studies still required to reveal the specific function of these molecules in the camel ON.     

Genetic analysis of optic nerve head coloboma in the Nova Scotia Duck Tolling Retriever identifies discordance with the NHEJ1 intronic deletion (collie eye anomaly mutation)

Collie eye anomaly (CEA) encompasses a spectrum of different ophthalmic phenotypes from clinically inconsequential choroidal hypoplasia to blindness from coloboma of the optic nerve head (ONH). A previous study found a 7.8‐kb deletion in intron 4 of the NHEJ1 gene to be associated with CEA. A genetic test based on this association is recommended for many breeds, including the Nova Scotia Duck Tolling Retriever (NSDTR). Collection of ONH coloboma‐affected NSDTR showed lack of concordance of the NHEJ1 intronic deletion with ONH coloboma. Using genomewide single nucleotide polymorphism (SNP) genotyping in 7 ONH coloboma‐affected NSDTR cases and 47 unaffected NSDTR controls with no ophthalmic signs, one SNP, located on chromosome 7, demonstrated genomewide significance. However, high genomic inflation may have confounded the results. Therefore, the genomewide association study was repeated using EMMAX to control for population structure in the cohort of 7 cases and 47 controls. However, no regions of the genome were significantly associated with ONH coloboma. These results failed to document significant association with the CEA locus. Due to the complex genetic etiology of ONH coloboma, the NHEJ1 intronic deletion test results should be carefully considered when making breeding decisions. If the goal is to select for visually competent dogs, our data suggest that eye examinations of puppies would be more effective as a guide in selection of breeding pairs than relying solely on currently available genetic tests.     

Ultrasonographic appearance of the craniocervical junction in normal brachycephalic dogs and dogs with caudal occipital (Chiari-like) malformation

Ultrasonographic evaluation of the spine, especially of the spinal cord, has been rarely reported in dogs. The atlanto-occipital junction provides a small acoustic window through which examination of the craniocervical transition can be performed. Normal sonographic findings of this region in 10 normal brachycephalic dogs are presented and compared with sonographic findings from 25 Cavalier King Charles Spaniels with the caudal occipital malformation syndrome. Sonographic findings were compared with magnetic resonance imaging findings to determine the extent of cerebellar herniation and syringohydromyelia. Cerebellar displacement into the foramen magnum was clearly identified sonographically; however, syringohydromyelia was not discernable due to bone overlay.     

Spontaneous adenocarcinoma with giant cell formation in the accessory sex glands in a male Sprague-Dawley rat

In this study, we report the features of an adenocarcinoma with giant cell formation spontaneously occurring in the accessory sex glands of a male 10-month-old Sprague-Dawley rat. A milky white mass was found in the region corresponding to the left seminal vesicle and the left coagulating gland. Histologically, tumor cells exhibited diverse growth patterns, including glandular/trabecular, cystic, and sheet-like growth areas. The tumor cells were pleomorphic, with round- or oval-shaped nuclei and abundant eosinophilic cytoplasm. Mitotic figures were occasionally observed. Giant cells were also prominent in the sheet-like growth area, with intracytoplasmic vacuoles containing eosinophilic material. The stroma was rich in collagen fibers and fibroblasts. Numerous inflammatory cells were observed in the glandular and cystic lumina and stroma. Immunohistochemically, the tumor cells were positive for cytokeratin AE1/AE3 and proliferating cell nuclear antigen. In the sheet-like growth area, some of the tumor cells and giant cells were positive for vimentin in the cytoplasm adjacent to the nucleus. Electron microscopy revealed that the tumor cells contained a small number of mitochondria and rough endoplasmic reticulum, and had no basement membrane or desmosome. The giant cells occasionally contained variably sized intracytoplasmic lumina and globular filamentous bodies, probably corresponding to vimentin. Considering these morphological features, the tumor was diagnosed as an adenocarcinoma with the formation of giant tumor cells originating from the male accessory sex glands.     

Congenital hypoplasia of the dorsal colon in a Quarter Horse filly with chronic,intermittent colic

Congenital colonic anomalies are rare in the horse and, to the authors' knowledge, no cases have been reported that include measurements of each segment of the large colon to confirm which section is abnormal. This case report describes chronic, intermittent colic in a Quarter Horse filly that had been attributed to chronic idiopathic hepatitis prior to an exploratory laparotomy. A colonic anomaly discovered at surgery became the primary differential for aetiology of the intermittent colic. Euthanasia of the filly and necropsy allowed further examination of the anomaly, where it was determined that the dorsal colon was short compared to the ventral large colon. In addition, the diagnosis of chronic idiopathic hepatitis was confirmed.     

A retrobulbar dermoid cyst with involvement of the sinus in an 18-year old pony

This case report describes a retrobulbar dermoid cyst in an 18-year-old pony with an invasive character into the frontal sinus. CT imaging was important for the appropriate management of this case and the definitive diagnosis was obtained from histopathology. Surgical excision was performed successfully without recurrence 1-year post-operatively. The pony returned to its intended use and previous performance level, although complaints of mild symptoms of headshaking were noted in bright light only.     

The problems of X-ray image formation in veterinary practice--result of a cyclic study with the use of a test phantom for the determination of image quality

To grasp the problems of producing X-ray pictures in veterinary surgery, a ring trial was carried out. The task of the veterinarians was to produce two radiographs: from a certain body region, together with a test phantom, which allowed the judgement of the image quality immediately. The dates and technique of exposure had to be chosen as usual, one picture had to be developed in the dark room, either manually--the usual way with the normally used chemicals or by automatic developing machine. The other picture was developed under standard conditions in the Institute of Medical Physics. For a third radiograph, already exposed with the correct dose, only development was requested. Therewith the total process of producing an x-ray picture, the exposure dates and -technique and the dark-room procedure should be analyzed. Additionally a protocol was drawn up. All results were treated anonymously. The outcome of the trial obviously showed the problems: blatant tendency to overexposure, in no case underexposure, combined with faults in the dark room--e.g. disregarding the condition of the developer or the probably given necessity of changing the developer and even the importance of controlling time and temperature during developing. No informations were requested about fixation- and stop bath or the method of drying.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative Doppler imaging of the ophthalmic vasculature in normal Beagles and Beagles with inherited primary open-angle glaucoma

The objective of this study was to compare orbital and ocular vasculature velocity, measured by Doppler imaging, in normal Beagles and Beagles with inherited primary open-angle glaucoma. Eight normal Beagles and 13 Beagles with different stages of primary open-angle glaucoma were evaluated twice with a 2–4-week period between measurements. Doppler imaging was performed with the dogs anesthetized, and the Doppler transducer applied directly on the corneal surface. The majority of the orbital vasculature (external ethmoidal artery; internal ophthalmic artery and vein; and external ophthalmic artery and vein) and ocular blood vessels (anterior ciliary artery and veins; long posterior ciliary arteries; short posterior ciliary arteries; primary retinal arteries; and the vortex veins) were identified and Doppler blood velocity parameters were determined. The glaucomatous dogs demonstrated significant differences in the Doppler velocity parameters of several orbital vessels (external ethmoidal, external ophthalmic, and internal ophthalmic arteries), and several ocular vessels (anterior ciliary, short posterior ciliary, and long posterior ciliary arteries). These differences included decreased blood velocities, and increased pulsatility and resistive indexes. The Doppler blood flow velocities of the primary retinal arteries were unchanged between the normal and glaucomatous dogs. In the glaucomatous dogs, the Doppler imaging suggests increased vascular resistance downstream in both the orbital and ocular vasculature. These blood velocity parameter changes may be primary or secondary, and may offer therapeutic opportunities to increase perfusion, prolong the retina and optic nerve head function, and maintain vision in the canine glaucomas.     

Lymphangiosarcoma with bone formation of the auricle in a dog

A 12-year-old mixed-breed neutered female dog was referred with cutaneous tumors at the left auricle. Histologically, the cutaneous tumor located in the dermis comprised numerous clefts and cavernous channels lined by neoplastic endothelial cells with no erythrocytes. Bone tissue without direct contact with neoplastic cells was seen in the well-developed stromal connective tissue. The neoplastic endothelial cells exhibited mild to moderate atypia. Immunohistochemically, neoplastic cells were positive for vimentin and negative for cytokeratin and factor VIII-related antigen. Basement membrane around the neoplastic lumens was positive for laminin in a linear or granular pattern. Ultrastructural examination revealed discontinuous basement membrane beneath the tumor cells. Histopathological features of this case were consistent with lymphangiosarcoma, and stromal ossification was characteristic.