Nictitating Membrane Research Articles

Effects of pharmacology with acepromazine maleate in tranquilization, hematology and vital parameters in cats

This work aims to evaluate the tranquilization, the hematological and the physiological parameters of domestic cats undergoing pharmacupuncture with acepromazine maleate. Seven animals received 5% of the dose of the drug indicated for this species in acupoint Yintang (GI) and seven (GII) received the same dose intramuscularly. The reassurance was assessed using a scale adapted from Dobbins et al. (2002). The GI group demonstrated that 71.43% of the animals presented drowsiness and projection of the third eyelid and 28.47% were less active. In GII group, 14.28% of cats were less active and 85.72% demonstrated were unchanged. About the hematologicals changing, the two groups demonstrated a slight increase of leukocytes, in GI decreased hematocrit and erythrocytes. According to physiological parameters, GI presented decrease rectal temperature and increase in respiratory rate. There were no significant changes on the heart rate and systolic blood pressure in any cat. In GII, occurred a decrease in diastolic blood pressure. The pharmacupunture showed effectiveness in cats tranquilization, besides clinical safety.

Preoperative indicators of failure of en bloc resection or perforation in colorectal endoscopic submucosal dissection: implications for lesion stratification by technical difficulties during stepwise training

The technical difficulties inherent in endoscopic submucosal dissection (ESD) for colorectal neoplasms may result in the failure of en bloc resection or perforation. The aim of this retrospective study was to assess the predictors of en bloc resection failure or perforation by using preoperatively available factors. Between September 2002 and March 2013, 716 colorectal ESDs in 673 consecutive patients were performed at a tertiary cancer center. Patient characteristics, tumor location, tumor type, colonoscopy-related factors, and endoscopist experience were assessed based on a prospectively recorded institutional ESD database. Logistic regression analysis was performed to identify predictors of failure of en bloc resection or perforations, with subgroup analyses of ESDs performed by endoscopists less experienced in colorectal ESD (<40 cases) and for colonic lesions only. On multivariate analysis, independent predictors of failure of en bloc resection or perforations were the presence of fold convergence (odds ratio [OR] 4.4; 95% confidence interval [95% CI], 1.9-9.9), protruding type (OR 3.6; 95% CI, 1.8-7.1), poor endoscope operability (OR 3.5; 95% CI, 1.8-6.9), right-sided colonic lesions (OR 3.0; 95% CI, 1.5-6.3 vs rectal lesions), left-sided colonic lesions (OR 3.2; 95% CI, 1.7-6.3, vs rectal lesions), the presence of an underlying semilunar fold (OR 2.1; 95% CI, 1.3-3.6), and a less-experienced endoscopist (OR 2.1; 95% CI, 1.3-3.6). Among less-experienced endoscopists, colonic lesions were independent predictors (right-sided colonic lesions 8.1; 95% CI, 2.9-25.1; left-sided colonic lesions 8.1; 95% CI, 2.5-28.3 vs rectal lesions). For colonic lesions, the presence of fold convergence (OR 3.7; 95% CI, 1.6-8.6), poor endoscope operability (OR 3.6; 95% CI, 1.8-7.2), a less-experienced endoscopist (OR 3.0; 95% CI, 1.7-1.8), and the presence of an underlying semilunar fold (OR 2.7; 95% CI, 1.5-4.7) were identified predictors. This study successfully identified predictors of en bloc resection failure or perforation. Understanding these indicators could help to accurately stratify lesions according to technical difficulty and to appropriately select endoscopists.

Ocular manifestations of canine transmissible venereal tumour: a retrospective study of 25 cases in Greece

Transmissible venereal tumour (TVT) is a sexually transmitted neoplasm that frequently affects dogs of either sex, in tropical and subtropical regions. TVT primarily involves the external genitalia, although extragenital sites...

Third eyelid gland neoplasms of dogs and cats: a retrospective histopathologic study of 145 cases.

To describe the various types of primary neoplasms affecting the third eyelid (TEL) gland of dogs and cats. A retrospective search of the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) database was performed. Veterinary ophthalmologists, primary care veterinarians, and, when appropriate, owners were contacted for patient follow-up information. Patient data points collected included species, age, sex, breed, laterality, tumor type, surgical margins, recurrence, metastasis, and length of follow-up. A total of 127 canine and 18 feline cases met the inclusion criteria. The most common canine TEL gland tumor was adenocarcinoma (n=108; 85.0%) followed by adenoma (n=18; 14.2%) and squamous cell carcinoma (SCC) (n=1; 0.8%). For canine cases with follow-up information available (n=62), 8.1% had confirmed or suspected metastasis and 11.3% had confirmed or suspected local recurrence of disease. The most common feline TEL gland tumor was adenocarcinoma (n=15; 83.3%) followed by SCC (n=3; 16.7%). For feline cases with follow-up information available (n=9), 40.0% had confirmed or suspected metastasis and 30.0% had confirmed or suspected local recurrence of disease. This study determined that adenocarcinoma was the most common third eyelid gland tumor in both dogs and cats. The overall survival times were less, and metastatic occurrence and recurrence rates appeared to be higher for feline tumors as compared to those diagnosed in dogs. This is the first report of SCC originating from glandular ductular epithelium.

Clinical and histologic description of ocular anatomy in captive black‐tailed prairie dogs (Cynomys ludovicianus)

To describe the clinical and histologic ocular anatomy of the black-tailed prairie dog (PD). Seventeen captive black-tailed PDs (11 males and six females), ranging in age from approximately 4months to 4.5years. Complete ocular examinations, including slit-lamp biomicroscopy, direct and indirect ophthalmoscopy, were performed under isoflurane anesthesia. The globes (n=2) of one black-tailed PD were harvested immediately after euthanasia and processed after formalin fixation. Staining with hematoxylin-eosin, cytokeratin AE1/AE3, glial fibrillary acidic protein, chromogranin A, claudin-5, smooth muscle actin, and vimentin was performed for light microscopic evaluation. A thick mucinous precorneal tear film was present on the ocular surface. A vestigial nictitating membrane was identified in the medial canthus area. The limbus was heavily pigmented, the iris was a dark homogenous brown, and the pupil was round. Funduscopically, there was no tapetum lucidum, the retinal vascular pattern was holangiotic, and a horizontally elongated optic disk was visualized. The most common ocular abnormalities were acquired eyelid margin defects, present in seven eyes of six black-tailed PDs (35.3%). On histologic examination, the retina was asymmetric, thicker below the optic disk and thinner above it. The black-tailed PD fundus is atapetal with a holangiotic retinal vessel pattern and a horizontally elongated optic disk. Acquired lesions of the peri-ocular and eyelid region were the most common documented abnormality. Unique anatomic features of the globe and adnexa were confirmed with histologic and immunohistochemical analysis.

Third eyelid in the small Indian mongoose (Herpestes javanicus): a morphological and histological study.

The Indian mongoose (Herpestes javanicus) is native to parts of Asia, Iran. The purpose of this study was to describe the gross anatomy of the cartilage and histology of the superficial gland of the third eyelid of two adult mongooses. The animals, in terminal stages of disease and near death due to aging or unknown reasons, were referred from Park Zoo (Shiraz, Iran) to our center. By using a modified maceration technique, the morphological characteristics of the cartilage were examined. For histological examinations of the superficial gland of the third eyelid, the samples were stained with haematoxylin and eosin. Also, to detect the elastic fibers in the cartilage sections were stained with orcein and Weigert's resorcin-fuchsin. The cartilage consisted of an ovoid appendix and a mild reverse sigmoid crossbar. Elastic fibers were scattered throughout the cartilage but were more concentrated in the center. The superficial gland of the third eyelid was compound tubuloacinar with serous acini.

Mycotic Keratitis in a Khaki Campbell Duck ( Anas platyrhynchos domesticus).

A 1.5-year-old, intact female khaki Campbell duck (Anas platyrhynchos domesticus) was evaluated for lethargy and a swollen left eye (OS). Mucoid discharge, chemosis, and conjunctival hyperemia with trace aqueous flare, indicating anterior uveitis, in the anterior chamber were evident on ophthalmic examination. There was no fluorescein stain uptake by the cornea. Initial topical antibiotic therapy and systemic anti-inflammatory treatments were unsuccessful, and the lesion progressed to a diffuse, yellow-white plaque, which covered 90%-95% of the cornea 4 days later. There was moderate blepharospasm, mild blepharedema, and epiphora OS. The mobility of the nictitating membrane was impaired because of the presence of the plaque over the cornea. Cytologic examination of a corneal scraping revealed fungal hyphae, and aerobic culture confirmed Aspergillus species. Treatment with topical voriconazole (1 drop OS q4h-q6h) was initiated and was switched to oral voriconazole (20 mg/kg PO q12h) 6 days after initiating treatment. The ocular disease improved during the antifungal treatment period. Eighty-four days after initial presentation (9 days after discontinuation of treatment), there was no clinical evidence of mycotic keratitis on ophthalmic examination.

Time course of the rabbit's conditioned nictitating membrane movements during acquisition, extinction, and reacquisition.

The present experiment tested whether or not the time course of a conditioned eyeblink response, particularly its duration, would expand and contract, as the magnitude of the conditioned response (CR) changed massively during acquisition, extinction, and reacquisition. The CR duration remained largely constant throughout the experiment, while CR onset and peak time occurred slightly later during extinction. The results suggest that computational models can account for these results by using two layers of plasticity conforming to the sequence of synapses in the cerebellar pathways that mediate eyeblink conditioning.

Saving their skins: how animals protect from the sun.

Adistinctive evolutionary changeexperiencedbyour ancestors as they branched away from their fellow apes was the loss of body hair. While this may have had certain benefits, our species has also suffered drawbacks; forone,without thick furorhair toscattersunlight,ourskin ismore susceptible to burning in the sun. Indeed, sunburns have been observed in other relatively hairless members of the animal kingdom, including whales, dolphins, fish, elephants, and rhinoceroses. But just as humans have evolved physiologic and behavioral adaptations to protect from the sun, other creatures too have developed their own. Whaleshavehairless, streamlinedbodiesand frequently travel to the sea surface for air, making them particularly vulnerable to UV-induced skin damage. The spermwhale,which spends up to6 hours at a time at the surface, is known to activate genotoxic stress pathways in response to persistent UV exposure. While the fin whale possesses constitutivelyhigh levelsofmelanin, thebluewhalemodulates its skinmelanin throughout the year, becoming darker when UV levels are highest from February to May. This adaptive pigmentation has also been observed in hammerhead sharks and some fish. EquatorialAfrica,which receivesabundantdaily sunlightyear round, is home to theworld’s 3 largest pachyderms: the elephant, rhinoceros, andhippopotamus, forwhomlearnedbehaviorsareessential forsunprotection.TheAfricanelephantuses itsprehensile trunkto throwdustonto itsback, the rhinoceroswallows inandcoats itselfwithmud,and thehippopotamus submerges itself in water. The hippopotamus also possesses a curious adaptation found in no other animal—it manufactures its own sunscreen. The hippopotamus’s “blood sweat” is a thick, reddish fluid that is neither blood nor true sweat, as the animal’s skin contains no sebaceous glands. It is secreted by subdermal glands through large skinpores andcontains2pigments, hipposudoric acid andnorhipposudoric acid, whose polymerization gives the fluid a reddish orange color and whose absorption of UV light makes this substance a highly effective sunscreen. Someanimalsarewell coveredwith furbutmayneedtoprotectother body parts from the sun. A giraffe’s long tongue, frequently outstretchedtoforagethetreetopsfor leaves, iscoloredblackishpurple from thecircumvallatepapillae to the tip,believedtoprotect it fromsunburn. The meerkat’s eyes are surrounded by dark bands to reduce sun glare, and the nictitating membrane covering a polar bear’s eye filters bright sunlight reflected by the snow. Increasing UV exposure from a depleted ozone layer will certainly exert a selective pressure on animals to evolvemore sophisticated skin defenses. Studying thesecreaturesmayprovidegreater insight into skin physiology and how our own species will adapt to a changing solar environment.

Avian reflex and electroencephalogram responses in different states of consciousness

Defining states of clinical consciousness in animals is important in veterinary anaesthesia and in studies of euthanasia and welfare assessment at slaughter. The aim of this study was to validate readily observable reflex responses in relation to different conscious states, as confirmed by EEG analysis, in two species of birds under laboratory conditions (35-week-old layer hens (n=12) and 11-week-old turkeys (n=10)). We evaluated clinical reflexes and characterised electroencephalograph (EEG) activity (as a measure of brain function) using spectral analyses in four different clinical states of consciousness: conscious (fully awake), semi-conscious (sedated), unconscious-optimal (general anaesthesia), unconscious-sub optimal (deep hypnotic state), as well as assessment immediately following euthanasia. Jaw or neck muscle tone was the most reliable reflex measure distinguishing between conscious and unconscious states. Pupillary reflex was consistently observed until respiratory arrest. Nictitating membrane reflex persisted for a short time (<1min) after respiratory arrest and brain death (isoelectric EEG). The results confirm that the nictitating membrane reflex is a conservative measure of death in poultry. Using spectral analyses of the EEG waveforms it was possible to readily distinguish between the different states of clinical consciousness. In all cases, when birds progressed from a conscious to unconscious state; total spectral power (PTOT) significantly increased, whereas median (F50) and spectral edge (F95) frequencies significantly decreased. This study demonstrates that EEG analysis can differentiate between clinical states (and loss of brain function at death) in birds and provides a unique integration of reflex responses and EEG activity.

Exceptional soft tissue fossilization of a Pleistocene vulture (Gyps fulvus): new evidence for emplacement temperatures of pyroclastic flow deposits

Volcanic sediments are often unsuitable for the fossilization of both hard and soft organic tissues, however, in some circumstances, they can provide unusual conditions for the preservation of remains. Here we report an exceptional case of soft tissue fossilization of a Late Pleistocene Eurasian griffon vulture (Gyps fulvus) in the pyroclastic sequence of the Alban Hills volcanic region (SE Rome, Italy). CT analyses have revealed an exceptional natural cast of the complete head and neck that preserve extraordinary detail including the fossilized everted tongue, beak, feather insertions and the first record of the nictitating membrane of the eye. This fossilization (superior in detail even to the victims of the AD 79 Plinian eruption of Vesuvius) reveals no evidence of burning and requires re-evaluation of the thermal constraints in operation for the preservation of organic materials within pyroclastic sediments. The analysis of the external morphological features has provided key information regarding the taphonomic processes in operation, the emplacement temperatures of distal pyroclastic flow deposits and the relationships between organic materials and low temperature phreatomagmatic flows. This sheds light not only on the extremely rare situation of fossilization in volcanic contexts but also provides a new perspective on taphonomic studies of highly detailed casts of fossil vertebrates.

A New Nonhuman Primate Model of Severe Dry Eye

The aim of this study was to establish a new rhesus monkey model of severe dry eye. A total of 8 rhesus monkeys were used for the study. Four monkeys had their main lacrimal gland and nictitating membrane surgically removed (group 1). Another 4 monkeys had a similar surgery with further application of 50% trichloroacetic acid on the bulbar conjunctiva (group 2). The ocular surface was evaluated before and after the surgery (1, 4, 8, 12, and 24 weeks) using Schirmer-1 test, corneal fluorescein staining, and the lissamine green test. Conjunctival impression cytology was also performed before and 24 weeks after the surgery. Finally, the cornea and the conjunctiva were evaluated using light microscopy. A significant decrease in tear secretion was observed in all operated eyes. Schirmer test data measured were ≤4 mm in all the operated eyes. Slit-lamp examination also revealed abnormal staining in all the operated eyes that remained stable until the end of the experiment. In group 2, corneal fluorescein staining and lissamine green test values were always ≥5 (max 12) and ≥4 (max 9), respectively. Impression cytology specimens of both the treated groups showed conjunctival squamous metaplasia and a decreased number of goblet cells. Under light microscopy, the corneal epithelium appeared irregular with edematous basal epithelial cells. The conjunctiva showed a decreased goblet cell density with infiltration of inflammatory cells. Complete removal of the principal lacrimal gland and nictitating membrane associated with the application of 50% trichloroacetic acid on the conjunctiva could induce severe dry eye in rhesus monkeys.

Unusual presentation of a T-cell-rich large B-cell lymphoma in the nictitating membrane in a seven-year-old Bavarian warmblood gelding

A seven-year-old, 550-kg, Bavarian warmblood gelding was referred to the Ophthalmology Service of the Veterinary University Vienna, due to a mass on the bulbar aspect of the nictitating membrane of...

Through the Looking Glass: The Spectacle in Gymnophthalmid Lizards

The anatomy and development of the eyelids in squamate reptiles are still relatively unknown, considering its variation within the group. The neotropical Gymnophthalmini are traditionally characterized by having lost the eyelids, but their structure is not well described. In this study, the embryonic development and the adult morphology of the gymnophthalmid eye, with special attention to the eyelids, the nictitating membrane, and the spectacle are described. The eye in some Gymnophthalmini is covered by a spectacle, formed by the embryonic fusion of the dorsal and ventral eyelids, a character possibly synapomorphic to the tribe. The genus Tretioscincus, which floats either as sister to all other Gymnophthalmini, or is nested within the group, is unique in showing functional and movable eyelids. Thus, the presence of functional eyelids can be either considered as the primitive condition for the gymnophthalmini or as a re-acquisition of the character, showing the importance of a well-established phylogenetic hypothesis for understanding morphological evolution.

Chapter 4 - Distribution of Neural Plasticity in Cerebellum-Dependent Motor Learning

The cerebellum is essential for some forms of motor learning. Two examples that provide useful experimental models are modification of the vestibulo-ocular reflex and classical conditioning of the nictitating membrane response (NMR) in the rabbit. There has been considerable analysis of these behavioral models and of conditioning of the eyelid blink reflex, which is similar in several respects to NMR conditioning but with some key differences in its control circuitry. The evidence is consistent with the suggestion that storage of these motor memories is to be found within the cerebellum and its associated brainstem circuitry. The cerebellum presents many advantages as a model system to characterize the cellular and molecular mechanisms underpinning behavioral learning. And yet, localizing the essential synaptic changes has proven to be difficult. A major problem has been to establish to what extent these neural changes are distributed through the cerebellar cortex, cerebellar nuclei, and associated brainstem nuclei. Inspired by recent theoretical work, here we review evidence that the distribution of plasticity across cortical and cerebellar nuclear (or brainstem vestibular system) levels for different learning tasks may be different and distinct. Our primary focus is on classical conditioning of the NMR and eyelid blink, and we offer comparisons with mechanisms for modifications of the vestibulo-ocular reflex. We describe a view of cerebellar learning that satisfies theoretical and empirical analysis.

Detection of Polyps Including Adenomas in the Ascending Colon by Cap-assisted Chromocolonoscopy with Indigo Carmine.

Adenomatous polyps are precursors of colorectal cancer, and their removal is important because it could potentially reduce the incidence and mortality of colorectal cancer. These concepts have formed the basis for the removal of adenomatous polyps after detection.1 Nonpolypoid adenomas, which are at an increased risk of developing into colorectal cancer, are difficult to detect during routine colonoscopy, and small adenomas may be missed during colonoscopy.2 Cap-assisted colonoscopy and chromocolonoscopy have emerged as techniques with the potential to improve the detection of colon polyps. Cap-assisted colonoscopy uses a transparent plastic hood attached to the tip of the colonoscope to flatten the semilunar folds and improve mucosal exposure.3 A systemic research and meta-analysis of 12 studies that have examined the usefulness of cap-assisted colonoscopy for polyp detection found that cap-assisted colonoscopy was associated with improved detection of colorectal polyps.3 Chromocolonoscopy is a colonoscopic examination performed using the indigo carmine spray technique. Togashi et al.4 described that chromocolonoscopy increased the detection of neoplastic polyps and flat adenomas, particularly diminutive polyps, but did not increase the detection of advanced lesions.4 Hashimoto et al.5 showed that the adenomatous polyp detection rate of chromocolonoscopy was not better than that of standard colonoscopy. Thus, whether chromocolonoscopy using indigo carmine increases the detection of colorectal polyps remains controversial.4,5 Additional indigo carmine spraying during cap-assisted colonoscopy is expected to improve the detection rate of colon polyps, especially adenomatous polyps. Therefore, this study aimed to evaluate the usefulness of cap-assisted chromocolonoscopy in the proximal colon for routine colonoscopic examinations.6 Hood cap-assisted colonoscopic examination was first performed, followed by hood cap-assisted chromocolonoscopy with 0.2% indigo carmine, from the cecum to the hepatic flexure. The total number and characteristics of polyps were compared before and after spraying indigo carmine. Cap-assisted chromocolonoscopy was performed in 86 consecutive patients. Before indigo carmine spraying, a mean of 0.56 polyps per patient and 0.29 adenomas per patient (52% of the polyps) were found. After spraying of the dye, a mean of 0.62 polyps and 0.22 adenomas (36% of these additional polyps) were found additionally. Most (85%) of these additional polyps found after spraying were small (<0.5 cm). In total, a mean of 1.17 polyps and 0.51 adenomas (44% of total polyps) were found before and after spraying of the dye. In this study, hood cap-assisted chromocolonoscopy using indigo carmine showed a higher detection rate of polyps (especially, small polyps <0.5 cm) and adenomas in the ascending colon than cap-assisted colonoscopy without spraying of the dye. It is unclear whether cap-assisted chromocolonoscopy can increase the detection rate of polyps and adenomas compared with chromocolonoscopy without cap. This study has some limitations. It was a single-institution analysis, and a limited number of patients were included. Because only one laterally spreading tumor and one polyp >1 cm were observed in this study, the detection rate of laterally spreading tumors or large polyps could not be analyzed. The clinical significance of these small adenomas that can be found only after spraying a contrast agent needs to be further investigated.2

Effect of vagus nerve stimulation on electrical kindling in different stages of seizure severity in freely moving cats

Vagus nerve stimulation (VNS) is an adjunctive therapy for treating pharmacoresistant epilepsy. The present study analyze the effect of VNS on the epileptic activity of amygdala kindling (AK) in different seizure severity stages in freely moving cats. Fourteen adult male cats were used and were stereotaxically implanted in both amygdalae, in thalamic reticular nuclei and in prefrontal cortices. AK was developed by the application of 60Hz pulse trains that were one second in duration. VNS was applied the following day after the first stages were reached. This stimulation consisted of 10 pulse trains in the one-hour period (1min on/5min off) prior to AK. AK stimulation continued until all animals reached stage VI. The behavioral changes induced by VNS were transient and bearable. The animals showed relaxation of the nictitating membrane, ipsilateral anisocoria, swallowing and licking. Intermittent VNS application in stage I induced a delay in AK progression. The effect of VNS on the amygdala afterdischarge duration (AD) did not change progressively. VNS in stages II, III, and IV does not have an inhibitory effect on AK, and the AD further exhibited a progressive development. At the end of the generalized seizures, the animals presented with synchronized bilateral discharges of the spike-wave type (3Hz) and a behavioral "staring spell". Our results show that VNS applied during the different stages of seizure severity exerts an anti-epileptogenic effect in stage I but no anti-epileptogenic effect in stages II, III, and IV. These results suggest that VNS applied at stage I of kindling induces a delay of generalized convulsive activity.

Dacryocystography in a cat with orbital pneumatosis

A 2-year-old neutered male European short-haired cat was presented for a persistent discharge from the scar of previous left eye enucleation, performed 6 months prior by the referring veterinarian. A surgical exploration of the orbit was performed and retained nictitating membrane glandular and conjunctival tissues were removed. Eleven days later, the cat developed an orbital pneumatosis caused by retrograde movement of air through a patent nasolacrimal system and diagnosed by survey radiographic examination of the skull. Nasolacrimal system patency was assessed by dacryocystography performed by injection of iodinated contrast medium under pressure into the orbital cavity. Computed tomography dacryocystography confirmed the radiographic findings. The condition resolved following dacryocystography, possibly as an inflammatory response to the contrast medium. To our knowledge, this is the first case of orbital pneumatosis reported in a cat.

Dietary cholesterol degrades rabbit long term memory for discrimination learning but facilitates acquisition of discrimination reversal

We have shown previously that feeding dietary cholesterol before learning can improve acquisition whereas feeding cholesterol after learning can degrade long term memory. To examine these different findings within a single paradigm, we fed groups of rabbits 2% cholesterol or normal chow with or without 0.12ppm copper added to the drinking water following two-tone discrimination learning of the nictitating membrane response in which a 8-kHz tone (conditioned stimulus, CS+) was followed by air puff and a 1-kHz tone (CS−) was not. After eight weeks on the diet, we assessed the rabbits’ conditioned responding during testing and retraining. We then reversed the two-tone discrimination and assessed responding to the 1-kHz tone CS+and the 8-kHz CS−. During testing, rabbits given cholesterol without copper had lower levels of responding to CS+than rabbits in the other groups suggesting they did not retain the discrimination as well. However, during a brief discrimination retraining session, their response levels to the CS+returned to the level of the other groups, demonstrating a return of the memory of the original discrimination. At the end of discrimination reversal, these same rabbits exhibited superior discrimination indexed by lower response levels to CS− but similar levels to CS+, suggesting they were better able to acquire the new relationship between the two tones by inhibiting CS− responses. These results add to our previous data by showing cholesterol diet-induced degradation of an old memory and facilitation of a new memory can both be demonstrated within a discrimination reversal paradigm. Given discrimination reversal is a hippocampally-dependent form of learning, the data support the role of cholesterol in modifying hippocampal function as we have shown previously with in vitro brain slice recordings.

Giant Conjunctival Nevus

Conjunctival nevus is the most common tumor of the ocular surface and we selected the largest nevi to evaluate for clinical features and outcomes. To describe the clinical features and outcomes of giant (≥10 mm diameter) conjunctival nevus. Retrospective case series of 618 patients with conjunctival nevus, 32 of which had giant conjunctival nevus, treated at an ocular oncology service between July 1, 1974, and June 30, 2012. Observation, excisional biopsy, and cryotherapy. Management, nevus recurrence, and nevus transformation into melanoma. Of 618 patients with conjunctival nevus, 32 (5%) were classified as having giant conjunctival nevus. The mean patient age at diagnosis was 34 years. Of those with giant conjunctival nevus, a history of an increase in nevus base or thickness was noted in 15 cases (47%) and an increase in color intensity in 2 cases (6%). The giant nevus involved cornea in 11 cases (34%), limbus in 23 (72%), bulbar conjunctiva in 31 (97%), fornix in 9 (28%), tarsus in 3 (9%), semilunar fold in 10 (31%), and caruncle in 7 (22%). The nevi had mean diameter of 16 mm and mean thickness of 2 mm. On slitlamp examination, intrinsic cysts were identified in 25 cases (78%), intrinsic blood vessels in 26 (81%), and feeder vessels in 22 (69%). Management included excisional biopsy with cryotherapy in 23 cases (72%) and observation in 9 cases (28%). Amniotic membrane graft reconstruction was used following excision in 3 cases (13%). Malignant melanoma developed within the giant nevus in 1 case after 23 years of observation. Postexcisional biopsy, nevus recurrence was detected in 4 cases (17%), pseudopterygium in 1 (4%), dry eye in 1 (4%), and eyelid blepharoptosis in 1 (4%). In an ocular oncology practice, giant conjunctival nevus represents 5% of conjunctival nevi. This benign tumor rarely transforms into conjunctival melanoma. Management alternatives include observation or wide excisional biopsy, cryotherapy, and reconstruction, possibly with amniotic membrane graft.