Regeneration of the Corneal Epithelium after Debridement of its Central Region: An Autoradiographic Study on Rabbits

Purpose: To investigate the proliferative behavior of the corneal and limbal epithelia after debridement on the central region of the rabbit cornea. Methods: After scraping a circular epithelial area, 5 mm in diameter, in the center of the cornea, (3)H-thymidine ((3)H-TdR) was injected intravitreally, and the rabbits killed from 1 to 49 days afterward. The cornea, together with the adjacent conjunctiva, was processed for autoradiography. Results: The regenerating epithelium at the center of the cornea exhibited high frequencies of labeled nuclei when compared to controls. The mitotic indexes for the limbus were comparable in experimental and control eyes. The unique basal stratum of the limbal epithelium exhibited quick proliferation and vertical migration in all eyes. Cells that remained labeled for four weeks or more were observed throughout the corneal epithelium, including its basal stratum, and this did not depend on epithelial damage. Conclusion: Corneal epithelium wounds are healed by sliding and proliferation of cells surrounding the epithelial gap without any evidence for the participation of the limbal epithelium. Daughter cells labeled with (3)H-TdR were visualized in all layers of the corneal epithelium up to 7 weeks after the DNA precursor injection. However, at this long interval, the only labeled cells in the limbus were in the suprabasal layers.

Proliferation of the vascular endothelium of the iris following total debridement of the corneal epithelium and limbal excision of rabbits

Background Damage to the corneal epithelium causes not only a reaction for its repair but also affects other parts of the cornea as well as different components of the anterior segment of the eye. The purpose of this investigation was to analyze the consequences, following epithelial and limbal damage, to the iris of rabbits (Oryctolagus cuniculus).Methods The corneal epithelium was thoroughly scraped followed by surgical excision of the limbus. Next, (3)H-thymidine ((3)H-TdR) was injected intravitreally both into the right (experimental) and left (control) eyes which had their anterior segments processed for autoradiography at intervals of 2, 7 and 21 days after surgery (three rabbits per interval). The irises were also examined with scanning-electron and confocal microscopy after Evans blue injection.Results There was a high frequency of labeling in the cells of the iris blood vessels in the experimental eye, particularly the endothelial ones. The ratio of labeled cells between experimental and control irises was 40:1, with a population of nuclei increasing by 25% and remaining labeled up to 21 days. There was also an increase in the volume of the iris vasculature as shown by confocal microscopy. The high labeling frequencies of the vascular cells were observed throughout the iris from the ciliary to the pupillary regions.Conclusions The lesions on the corneal epithelium elicit proliferation of the iris vascular cells, mainly its endothelium, as well as an early breakdown of the blood-aqueous barrier. The daughter cells resulting from the damage to the eye surface were detected up to 21 days after a single injection of (3)H-TdR, most likely due to their slow turnover. As a consequence of this proliferation, the vasculature of the iris increased in volume.

Morphological and autoradiographic studies on the corneal and limbal epithelium of rabbits

The investigation was centered on the morphological features of the conjunctiva-cornea transition (limbus) of the rabbit eye and the proliferative behavior of its epithelium. The eyes were processed for examination with light and electron microscopy, as well as for autoradiography after intravitreal injection of [H-3]thymidine ([H-3]TdR). At the sites of extraocular muscle insertion, the vascularization of the stroma extended to the peripheral cornea, and the limbal epithelium was thin with its basal stratum made up by clear cuboidal cells. In between the muscle insertions, the cuboidal clear cells, as well as the stroma blood vessels; were scarce. At the light microscope level, the basement membrane was distinct in the cornea but not in the limbus or the conjunctiva. Autoradiographs demonstrated that, at the limbus, the basal cells migrated very quickly to the suprabasal region and remained there up to the 28-day interval. Labeled cells were identified in all epithelial layers of the cornea, including the basal one, at 21 and 28 days but not in the limbal basal clear cells. The rate of renewal of conjunctival epithelium was similar to that observed for the transition with scarce clear cells. The high-resolution autoradiographs demonstrated that the basal cuboidal clear limbal cells exhibit a quick renewal and that they are not label-retaining cells. These latter ones were detected all over the corneal epithelium and in the suprabasal layers of the limbus up to 28 days, in physiological conditions, without the need of stimulation by damage to the corneal epithelium.

Morphological analysis of the corneal endothelium in eyes of dogs using specular microscopy

Foram estudados 20 olhos de 10 cães sem raça definida, machos e fêmeas com 6 anos de idade. A morfologia das células do endotélio da córnea foi analisada utilizando-se microscópio especular de contato. Foram estudadas as regiões central e periférica da córnea. de cada região da córnea foram realizadas três micrografias. de cada micrografia foram analisadas no mínimo 100 células endoteliais. Foram obtidos os valores do polimegatismo e pleomorfismo. O endotélio corneano de cães caracterizou-se por uma monocamada de células poligonais uniformes em tamanho e forma. A forma predominante das células endoteliais foi hexagonal. O índice de polimegatismo foi 0.22. Este estudo demonstrou que a morfologia das células do endotélio da córnea de cães é semelhante à observada em humanos.

Amastigota forms resembling Leishmania sp. on corneal ulceration in a dog: case report

Relata-se o caso de um cão com leishmaniose visceral apresentando lesões cutâneas, caquexia e úlcera de córnea. Realizou-se o diagnóstico parasitológico e sorológico por meio de exame do material da medula óssea e por imunofluorescência indireta, respectivamente. À citologia da úlcera corneana, visibilizaram-se formas amastigotas compatíveis com Leishmania sp.

Corneal epithelial inclusion cyst in a dog

Relata-se o caso de um cisto de inclusão epitelial em um cão macho, boxer, com 7 anos de idade. O cisto havia sido observado por trinta dias, era único, não congênito e apenas um olho estava acometido. Sete meses antes da consulta, o cão apresentou ulceração corneana indolente, tratada com ceratectomia e recobrimento de terceira pálpebra. O cisto foi removido através de ceratectomia superficial, seguida de enxerto conjuntival pediculado. A recuperação foi descomplicada e não houve recidiva após sete meses de pós-operatório.

Febre catarral maligna em bovinos do Mato Grosso do Sul e de São Paulo

São descritos a epidemiologia, os sinais clínicos, os achados de necropsia e a histopatologia de seis casos de febre catarral maligna (FCM) em bovinos de 5 fazendas localizadas nos estados de Mato Grosso do Sul e São Paulo. A doença ocorreu em bovinos de ambos os sexos e com idades variando de 4 meses a 11 anos. Os índices de morbidade variaram de 0,25% a 6.6% e a letalidade foi de 100%. A evolução clínica foi aguda (2-3 dias) em seis casos e crônica em um (3 meses). O diagnóstico presuntivo de FCM nos casos descritos neste relato foi baseado nos sinais clínicos, achados de necropsia e confirmados pela histopatologia. Os principais sinais clínicos nos casos agudos foram febre, corrimento mucopurulento pelas fossas nasais, opacidade da córnea, sialorréia, úlceras em várias superfícies mucosas e distúrbios nervosos. O bovino do caso crônico mostrou opacidade da córnea e distúrbios neurológicos. Os principais achados de necropsia incluíam hiperemia e lesões diftéricas em várias superfícies epiteliais e a histopatologia consistiu de vasculite, focos de infiltrado mononuclear multifocal em vários órgãos e necrose de superfícies epiteliais.

Scanning electron microscopy of the corneal endothelium of ostrich

Objetivou-se examinar a superfície posterior do endotélio corneano e realizar análise morfométrica das células endoteliais da córnea de avestruz (Struthio camelus) valendo-se da microscopia eletrônica de varredura. Avaliaram-se o número de lados, a área celular média, a densidade celular e o coeficiente de variação da área celular. O endotélio corneano de avestruz constitui-se de células poligonais uniformes em tamanho e forma, e com poucas interdigitações das bordas celulares. Visibilizaram-se microvilosidades na superfície celular. A área celular média foi de 269±18µm² e a densidade celular foi de 3717±240 células mm-2. O coeficiente de variação foi de 0,06 e o percentual de células hexagonais de 75%. Não foram observadas diferenças significativas entre os parâmetros avaliados entre os olhos esquerdo e direito. Este estudo demonstrou que o endotélio corneano de avestruz é semelhante ao descrito em outros vertebrados.

Experimental lamellar keratoplasty in rabbits using microfibrilar cellulose membrane: clinical, morphological and immunohistochemical findings

Avaliaram-se aspectos clínicos, histopatógicos e imunoistoquímicos da córnes de coelhos da raça Nova Zelândia adultos e machos em ceratoplastias lamelares com membrana de celulose microfibrilar. Trinta animais distribuídos em cinco grupos (n=6) foram estudados por até 60 dias de pós-operatório. A avaliação clínica revelou manifestações moderadas de edema, blefaroespasmo e fotofobia ao segundo dia, evoluindo para formas discretas ou ausentes a partir do sétimo dia, período em que se observou, clinicamente, reparo do defeito corneal. A histopatologia revelou uma fina camada de células escamosas, recobrindo a área lesada já aos sete dias, com discreto infiltrado de células polimorfonucleares. Observaram-se vasos no epitélio a partir do 15o dia, com regressão ao 48o dia. A marcação com o anticorpo Ki67 mostrou aumento de células em proliferação aos 15 dias no epitélio e aos 30 dias no estroma. Nesse período, ocorreram remodelamento e adesão epitealial. Considerando a boa integração do implante, admite-se a membrana de celulose como um bom material a ser utilizado em ceratoplastia lamellar.

Topical 1% Nalbuphine on corneal sensivity and epitheilization after experimental lamellar keratectomy in rabbits

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Morphometric analysis of the corneal endothelium of Yacare caiman (Caiman yacare) using scanning electron microscopy

The objective of this study was to examine the endothelial surface morphology and to perform morphometric analysis of the corneal endothelial cells of Yacare caiman (Caiman yacare) using scanning electron microscopy. Morphometric analysis with regard to polygonality, mean cell area, cell density and coefficient of variation of mean cell area was performed. Cell areas were measured using image analysis software. The normal corneal endothelium of Yacare caiman consisted of polygonal cells of uniform size and shape with interdigitations of the cell borders. Microvilli appeared as protrusions on the cellular surface. The average cell area was 270 +/- 24 mum(2) and the endothelial cell density was 3704 +/- 324 cells/mm(2). The coefficient of variation of cell area was 0.22. This study demonstrates that the Yacare caiman corneal endothelium is similar to those described in other vertebrates.

Combined corneal lipid and calcium degeneration in a dog with hyperadrenocorticism: a case report

Corneal degeneration may occur with a deposition of lipids or calcium, or both. Calcareous and lipid degeneration may be either primary or secondary, associated with systemic diseases such as primary hyperlipidemia, hyperlipidemia associated with hyperadrenocorticism, and hypothyroidism. The authors report a case of bilateral corneal lipid and calcium degeneration in a 7-year-old female Poodle with hyperadrenocorticism. The condition worsened with Lysodren(R) therapy but responded to surgical excision.

Lidocaine effects on corneal endothelial cell ultrastructure

The purpose of this study was to determine whether intracameral commercial lidocaine 2% induces alterations on the rabbit corneal endothelium. Forty white rabbits received different substances inside the anterior chamber: group (G)1, no substance; G2 and G3 received lidocaine 2% with preservative in aqueous solution; G4 and G5, lidocaine 2% with preservative in gel solution; G6 and G7, the anesthetic preservative (metilparahydroxybenzoate 0.1%); and G8 and G9, lidocaine 2% without preservative in aqueous solution. The animals from G2, 4, 6 and 8 were sacrificed after 1 h, and from G3, 5, 7 and 9 after 24 h after injection of the substance inside the anterior chamber. The corneas were clinically evaluated and assessed by transmission and scanning electron microscopy. G1, 2, 6, 7, 8 and 9 animals had very similar characteristics in clinical, ultrastructural and morphometric evaluations; the G3 and G4 animals showed discrete edema and one animal in G5 had intense corneal edema. We conclude that lidocaine 2% with preservative induces few ultrastructural alterations in the corneal endothelial cells.

Corneal endothelial cell morphology of normal dogs in different ages

Endothelial cell function is essential to maintain corneal transparency, but unfortunately the regenerative capacity of the endothelium is limited. There are only a few reports describing the effect of age on morphologic appearance of corneal endothelial cells of dogs. Studies of normal corneal endothelial cells in humans and dogs have shown a decrease in endothelial cell density (ECD) and an increase in pleomorphism and polymegethism with advancing age. The purpose of this study was to investigate the effect of age on ECD and endothelial cell morphology in dogs. A total of 30 dogs were divided into three groups (10 dogs/group) based on age: group 1 (2-12 months old), group 2 (24-72 months old), and group 3 (84 months or older). Corneas were processed for light and scanning electron microscopy. Results showed only difference in cell density between group 1 and groups 2 and 3, showing an initial decrease in cell density as the animal matured. Whereas there was significantly greater variation in cell size within the dogs in group 3 than there was within the other two groups, suggesting that there was increased polymegethism and pleomorphism with advancing age.