Biomedical subjects

Franck J Ollivier

Publications and source records attributed to Franck J Ollivier.

8 recordsLinked to original sources

PubMed2004

The precorneal tear film in horses: its importance and disorders.

The precorneal tear film (PTF) is of critical importance in the physiologic and pathologic findings of the cornea. Clinicians should recall that quantitative and qualitative disorders of the PTF can be a cause of corneal diseases as well as a clinical sign of ocular surface diseases. It is also important to consider that some systemic and topical treatments may affect the PTF volume and composition. Not all interactions are known at this time. There is a continued need for basic research into PTF components in healthy and diseased equine eyes, because much remains unknown. Until additional basic information about the biochemical composition and pH of the PTF as well as the interactions between equine corneal pathogens and specific PTF deficits becomes available, it will not be possible to define the cause and effect relations precisely between the various ocular surface diseases and deficiencies,excesses, and imbalances of PTF components. It is quite possible that a number of equine corneal diseases may be manifestations of qualitative PTF disorders.

Animals↗

PubMed2004

Matrix metalloproteinase inhibition in corneal ulceration.

The primary objective of current treatment strategies for infectious keratitis is to sterilize the ulcer as rapidly as possible with topically administered antibiotics. Ulcerative processes can proceed in some cases, despite the absence of microbes, as a result of remaining corneal and tear film MMPs. Combining antibiotic therapy with MMP inhibitors can speed corneal healing, because MMPs play an important role in corneal ulceration and stromal liquefaction. MMPs from the rabbit, horse, and human being are inhibited by metal-binding agents EDTA, NAC, and doxycycline as well as by the serum antiprotease alpha2-macroglobulin. It is not yet certain which proteinase inhibitor has the most favorable therapeutic index for clinical use, although we prefer serum because of its effects on multiple types of proteinases. The MMP inhibitors do have significant therapeutic promise in the treatment of corneal ulceration.

Animals↗

PubMed2004

Functional and structural analysis of the visual system in the rhesus monkey model of optic nerve head ischemia.

PURPOSE: A redistribution of neurochemicals has been identified in the visual cortex of monkeys with laser-induced glaucoma. Examined were functional, structural, and neurochemical changes to the retina, optic nerve, and central visual system in a nonhuman primate model of optic nerve head (ONH) ischemia caused by sustained unilateral administration of endothelin (ET)-1 to the optic nerve. METHOD: ET-1 or sham control solution was delivered by osmotic minipump to the retrolaminar region of one optic nerve of rhesus monkeys (Macaca mulatta) for 1.5 years. ONH topography and blood flow velocity were serially studied with scanning laser tomography and laser Doppler flowmetry, respectively. Retinal and cortical electrophysiologic measurements from pattern-derived stimuli were obtained quarterly. Immunohistochemistry was used to identify the distribution of calbindin (CB) and c-Fos labeled neurons in the visual cortex areas V1 and V2, and lateral geniculate nucleus (LGN). Retinal ganglion cell counts and optic nerve axon density were determined by light microscopy. RESULTS: No significant changes in retinal and ONH morphology, ONH blood flow velocity, and retinal and cortical pattern-derived functional activity were detected. Measurement of CB-positive cell density in V1 and V2 showed a significant decrease in CB labeling to the contralateral side of the ET-1-treated eye (P < 0.04). CB-positive cells were present in the magnocellular layers of the LGN with no differences noticed between the ET-1- and sham-treated eyes. c-Fos-labeled neurons were found in striate area V1 and extrastriateV2 of both groups. No c-Fos labeling was observed in the LGN. CONCLUSIONS: Administering ET-1 to the orbital optic nerve alters neuronal metabolic activity in the visual cortex in rhesus monkeys. Metabolic activity reductions in the visual cortex precede the ability to detect functional and structural alterations in the retina, ONH, and visual cortex in this animal model.

Animals↗

PubMed2003

Bacterial corneal diseases in dogs and cats.

Corneal diseases are very common in small animals. Corneal disease associated with bacterial agents is frequent in the dog and maybe less frequent in the cat. The medical history, important steps of the ophthalmic examination, and the ophthalmic diagnostic tests that are relevant in such corneal conditions are outlined. Bacterial corneal diseases in dogs and cats are most commonly considered in one of two categories--bacterial ulcerative keratitis and corneal abscesses. The clinical aspects of these two entities as well as the therapeutic strategies available for general practitioners and ophthalmologists are discussed. Ulcerative keratitis is frequent; it represents the most common ocular diseases in dogs and cats. Because some of these corneal ulcers can be very severe, progress rapidly, and therefore are sight threatening, the crucial steps of their diagnosis and management are stressed. The use of a magnification system, fluorescein dye, and corneal cytology and culture, if indicated, is necessary for diagnosis at an early stage of the disease. The treatment of bacterial ulcerative keratitis should eradicate the infection, reduce or stop the corneal destruction and support the corneal structures, control the uveal reaction and the pain associated with it, and minimize the scarring. The prognosis depends on the stage and the severity of the corneal ulceration, the etiology of the condition, and the therapeutic choice. A close follow-up of animals with corneal ulceration is highly recommended because corneal ulcers can progress rapidly.

Animals↗

PubMed2003

Evaluation of various compounds to inhibit activity of matrix metalloproteinases in the tear film of horses with ulcerative keratitis.

OBJECTIVE: To examine in vitro effects of various antiproteolytic compounds on activity of matrix metalloproteinase (MMP)-2 and -9 in the tear film of horses with active corneal ulcers. SAMPLE POPULATION: Samples of tear film obtained from the eyes of 34 horses with active ulcerative keratitis. PROCEDURE: Horses were sedated, and tear samples were collected from the lower fornix of 34 ulcerated eyes by use of capillary tubes. The protease inhibitors 0.2% EDTA, 0.1% doxycycline, 10% N-acetylcysteine (NAC), 0.1% solution of a modified dipeptide that contains hydroxamic acid (ie, ilomostat), 0.1% alpha1-proteinase inhibitor (PI), 0.5% alpha1-PI, and 100% fresh equine serum (ES) were used to treat pooled samples. Amount of latent and active MMP-2 and -9 was measured by optical density scanning of gelatin zymograms of treated and untreated tear samples. RESULTS: Pooled tear samples obtained from ulcerated eyes contained the latent and active forms of MMP-2 and -9. Compared with MMP activity in untreated samples, total MMP activity (sum of all bands detected) observed on the gelatin zymogram gels was reduced by 99.4% by EDTA, 96.3% by doxycycline, 98.8% by NAC, 98.9% by ilomostat, 52.4% by 0.1% alpha1-PI, 93.6% by 0.5% alpha1-PI, and 90.0% by ES. CONCLUSIONS AND CLINICAL RELEVANCE: We documented that EDTA, doxycycline, NAC, ilomostat, alpha1PI, and ES inhibited MMP activity in vitro. Because these compounds use different mechanisms to inhibit various families of proteases in the tear film of horses, a combination of these protease inhibitors may be beneficial for treatment of corneal ulcers in horses.

Acetylcysteine↗

PubMed2002

Technical issues in electrodiagnostic recording.

Electroretinogram (ERG) and visual-evoked potentials (VEPs) are used in veterinary ophthalmology to assess the functional integrity of the retina and the central visual pathway. The interpretation of altered electrophysiologic potentials in diseases can be of great diagnostic value, although it is important to be aware of technical factors and the limitations of these techniques which may result in over-interpretation and misinterpretation of the recordings, such that they are similar to those found in disease-related electrophysiologic changes. The recorded potentials represent the differences in voltage between the active and reference electrodes. The ground electrode serves as zero. A differential or instrumentation amplifier selectively amplifies signals of interest while rejecting noise. Differences between inputs are amplified, whereas common signals are rejected in a process called common mode rejection (CMR). In order for CMR to be most effective in reducing noise, the electrode impedances should be balanced. Filters are part of the differential amplifier as they remove unwanted noise of a certain frequency. The frequency bandwidth, or passband, is the range of frequencies between low- and high-frequency filter settings that are not filtered out. Major sources of noise that cause interpretation artifacts are power lines, amplifier noise, physiologic activity, electrochemical electrode noise and circular grounds. Noise reduction is achieved with high amplifier input impedance, balanced electrode impedances, CMR, filters and signal averaging. Maintaining electrodes in good condition, achieving proper contact between electrode and animal, and keeping electrode leads short aid in achieving noise reduction.

Animals↗

PubMedDate not supplied

Equine amniotic membrane transplantation for corneal ulceration and keratomalacia in three horses.

PURPOSE: Amniotic membrane has antifibrotic, anti-angiogenic and antiprotease properties. This retrospective study was designed to investigate the use of equine amniotic membrane transplants (AMT) at preserving vision, maintaining the structural integrity of the globe and maximizing cosmesis in equine eyes with corneal ulceration and severe keratomalacia. METHODS: Equine amnion had previously been aseptically harvested from a 12-year-old Thoroughbred mare during an elective Cesarean section. Sections of amnion were stored at -80 degrees C and thawed as needed. Records of equine cases at the University of Florida with keratomalacia that received an AMT without adjunctive conjunctival grafting were examined. Clinical description, details of medical and surgical treatment, globe survival and visual outcome were documented. Etiologies were determined by cytology, culture or histology. RESULTS: Three horses with corneal ulceration and severe keratomalacia received an AMT without conjunctival graft between December 2002 and April 2003. Pseudomonas spp. were cultured from all three eyes, with evidence of a concurrent fungal infection in two eyes. The three ulcers were 50, 72, and 76% of corneal diameter, and each one worsened in the face of aggressive medical therapy. In all three cases, the AMT sloughed over a 4 to 6-week period. At last follow-up, all three eyes receiving AMT were comfortable and receiving no medication, with light perception and an inconsistent location-dependent menace response. All three horses returned to their prior work. CONCLUSIONS: Results of a small number of equine AMT suggest that amnion can be used successfully to preserve both globe structure and limited vision, as well as optimize cosmesis, in horse eyes with corneal ulceration and severe keratomalacia.

Amnion↗

PubMedDate not supplied

Suspected ivermectin toxicosis in a miniature mule foal causing blindness.

A 9-week-old miniature mule foal presented to the Veterinary Medical Teaching Hospital for acute blindness, ataxia, and depression following an overdose of an over-the-counter ivermectin-based de-worming medication. Ophthalmic examination and electrodiagnostic evaluation eliminated outer retinal abnormalities as the primary cause of the bilateral blindness, implicating instead a central neurologic effect of the drug. With symptomatic and supportive care, the foal recovered fully and regained its vision.

Animals↗