Biomedical subjects
Publications and source records attributed to D M Maurice.
Rabbits are strapped to a specially shaped platform with their legs dangling over the sides. This system of restraint allows freer access to the eyes for examination than other methods and prevents the animal from injuring itself by kicking. The animals appear to be quite relaxed and show no signs of harm on release.
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Patients with visually significant corneal edema, secondary to endothelial dysfunction, before the development of scaring or vascularization, need only have the corneal endothelium replaced to restore corneal clarity. This fact, plus the lack of consistently available donor material, prompted us to evaluate tissue cultured corneal endothelim (TCCE) as a donor source. We have shown that TCCE, when transplanted, can regain normal morphology and physiologic function. To accomplish practical use of autologous stroma, a transparent gelatin membrane which can serve as substrate for endothelial growth in tissue culture, has been developed. This cellular membrane has been transplanted successfully in rabbits with good functional results. It is hoped that ultimately this technique can be developed for routine use in man.
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An enclosed system is described utilizing an osmotically driven pump to continuously deliver a solution to a variety of intraocular locations. The behavior of this system is illustrated by using it to measure the fluorescein turnover rate in the anterior chamber.
Cultured endothelial cells have been shown to regain their physiological function when replaced in the rabbit eye. Corneas were wiped free of native endothelium and seeded with cultured cells. After an incubation period, full-thickness buttons were cut from these corneas and transplanted into recipient animals. Clear grafts were obtained only when the donor cells were derived from cultures less than a month old. Light and scanning electron microscopy showed the endothelial cells of these grafts to be present as a slightly irregular monolayer on the posterior surface of the cornea. In corneas made edematous by benzalkonium chloride, the clear graft remained surrounded by thick and cloudy host tissue. In those grafts with 3H-thymidine--labeled cells, radioactivity was limited to the host tissue.
Biopsy of conjunctival goblet cells may be carried out by pressing a piece of Millipore filter on the conjunctival surface. This can then be stained with PAS and hematoxylin and observed under the microscope after the filter has been cleared with oil. Either spots of mucous corresponding to the openings of the goblet cells are seen, or the filter adheres to the surface and pulls off one or more layers of epithelial cells and goblet cells. The procedure can be carried out on the unanesthetized eye and does not cause discomfort.
An addition to the specular microscope is described which allows it to record the thickness of the excised cornea automatically as a function of time. The focus of the instrument is scanned mechanically through the tissue, and the position of the reflecting surfaces is detected by a photo-electric system and marked on a chart recorder. The system is able to follow thickness changes over periods of many hours and with an accuracy greater than obtainable by manual operation. This system has been helpful in the evaluation of a new medium which considerably extends the useful lifetime of the corneal endothelial fluid pump.
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1. A technique for isolating and perfusing the rabbit cornea is described, which allowed its thickness to be continuously measured under the microscope. The reversal of thickness of the cold-swollen cornea on perfusion with various solutions at 37 degrees C was studied.2. It was found that only a combination of adenosine and glutathione was able to reliably reverse the thickness to its normal value. This mechanism is sodium, bicarbonate, and oxygen dependent. Inhibitors of glycolysis or electron transport stop the reversal process.3. The findings are consistent with a need for an ATPase but are not capable of distinguishing among several possibilities for its regulation.