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Biomedical subjects

K Tsubota

Publications and source records attributed to K Tsubota.

At least 253 records · Page 14Linked to original sources
PubMed1989

Thermal cycling effects on the stored rabbit cornea.

Specular microscopy has proven itself a useful tool for evaluation of donor corneas. In many eye banks, corneas are stored at 4 degree C and warmed to room temperature for specular microscopic evaluation. On occasion it would be desirable to put the cornea back into storage provided there were no detrimental effects of the recooling and subsequent rewarming. The effects of repeated cooling and rewarming (thermal cycling) on the corneal endothelium were determined using rabbit corneas stored in M-K medium at 4 degree C. Some corneas were left in the refrigerator for a 7-day storage interval while others were removed daily, warmed to room temperature, evaluated morphologically and biochemically with the specular microscope and the redox fluorometer, respectively, and then placed back in the refrigerator. At the end of the 7-day storage period there were no statistically significant differences in either the biochemical signals or the specular appearance between thermally cycled corneas and corneas that were continuously stored at 4 degrees C for the same period of time. Repeated warming, specular microscopic observation, and cooling of the cornea appear not to be detrimental to the corneal endothelium.

Animals↗
PubMed1988

Noninvasive metabolic analysis of preserved rabbit cornea.

With the method of corneal redox fluorometry, the autofluorescence of reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) in rabbit corneal endothelium was measured as a function of storage time in McCarey-Kaufman (MK) medium and K-Sol medium. Measurements were started immediately after preparation of the corneal button, and the corneas were followed up for up to three weeks of storage. In both media, the PN/Fp ratio of the endothelium initially increased slightly in the first or second day and then began to decrease toward a level lower than baseline. This initial increase is possibly a result of an adaptive mechanism. The PN/Fp ratio maintained itself in the range of baseline values up to one week in MK medium but not in K-Sol medium. With scanning electron microscopy, the surface of the membrane and cell border were maintained for a three-week preservation period, and no apparent differences were found between the corneas stored in the two media. With transmission electron microscopy, the intracellular organelles appeared almost normal through one week of preservation in corneas stored in either media. During weeks 2 and 3, however, intracellular edema with increased endothelial thickness became prominent in the corneas stored in both media. Although no visual difference in the morphological features of the endothelium was apparent between corneas stored in either medium, computer-assisted morphometric analysis showed a statistically significant increase in the coefficient of variation of mean cell area for the corneas preserved in K-Sol medium but not for those preserved in MK medium.

Animals↗
PubMed1988

Corneal endothelial changes following minor trauma.

The healing processes that occur when corneal endothelial cells are subjected to only mild trauma are not known. To study these processes we have developed a system that enables only a few endothelial cells to be traumatized or destroyed under continuous specular microscopic observation in vitro. Experiments in which a small group of cells were traumatized by gentle wounding with a microglass tip produced an immediate and distinct dark area having the same size as the tip. Using this method we have produced and observed two types of wound by controlling the force of wounding. The first type of wound, produced by a gentle touch, recovered within 1 hr. The second type of wound, produced by moderate touch, took about 24 hr to recover completely from the trauma. In the second type of wound, we observed migration, elongation, coalescence and mitosis during the healing process. Histological examination revealed that in the first type of wound, the cells remained intact with no apparent damage seen by vital staining and light microscopy. For the second type of wound, the cells were completely missing although there was no apparent damage to Descemet's membrane.

Animals↗
PubMed1988

Effects of air and irrigating solutions on the corneal endothelium.

It is well established that the corneal endothelium reflects the trauma it experiences by changing its morphological appearance. We have studied the effect of mild trauma to the rabbit endothelium by replacing the aqueous humor with air. After either 2 or 4 h, the air was removed and then replaced with either physiological saline or balanced salt solution (BSS). Specular microscopy was then performed for 1 week to observe endothelial changes. Various transient morphological changes observed during this period included many nonhexagonal cells, enlarged cells, and clusters of small cells. The changes produced were more dramatic for the saline replacement group than the BSS replacement group, indicating that the recovery process of the endothelium following this mild trauma depends on the material used to replace the air. The air appears to sensitize the endothelium to subsequent insult. This model can perhaps be used to evaluate the relative safety of the various solutions that are used in the anterior chamber during ocular surgery.

Air↗
PubMed1987

Clinical features of a newly recognized type of lattice corneal dystrophy.

We examined five patients with an undescribed type of lattice corneal dystrophy. All patients were in the seventh to ninth decades of life and had developed decreasing vision late in life. None of the patients had suffered from recurrent epithelial erosions, there was no overt evidence of systemic amyloidosis, and the lattice lines were much thicker than those usually observed in lattice corneal dystrophy types I and II. Available pedigree data from two families of three patients indicated that the corneal disorder affected several siblings but not the parents or offspring. Two patients had no affected family members. There was no known consanguinity in any of the four families.

Adult↗
PubMed1987

Morphometric analysis of corneal endothelium following radial keratotomy.

We performed morphometric analysis of the central corneal endothelium on 24 eyes of 19 patients who had had anterior radial keratotomy. The endothelium was analyzed for a variety of parameters, including cell area, perimeter, side lengths, cell shape, and number of sides. Mean, standard deviation, and coefficient of variation were calculated for each parameter. The mean cell density decreased from 2,835 to 2,677 cells/mm2, mean cell perimeter increased from 71.4 micron to 74.3 micron, and mean side length increased from 11.8 micron to 12.3 micron following surgery. The changes in these three parameters were statistically significant (P less than 0.05). The coefficient of variation of cell area (polymegathism) changed from 0.319 to 0.307, the hexagonality changed from 62.5% to 59.6%, and the cell shape changed from 0.872 to 0.867. The changes in these parameters were not statistically different before and after surgery. The group of patients that had no reported microperforations showed only a small decrease of cell density (1.6%), while the group of patients that had microperforations showed a large decrease of cell density (14.3%). The cell perimeter and side lengths showed a similar pattern. The group of corneas with the optical zone diameter less than 3.5 mm showed a decrease in mean cell density from 2,994 to 2,725 cells/mm2, and the cell shape changed from 0.874 to 0.866 following surgery. The changes in these parameters were statistically significant (P less than 0.05) before and after surgery. Among all factors associated with radial keratotomy, microperforation and a small diameter of central optical zone appear to be the two greatest risk factors.

Adult↗
PubMed1987

Lattice dystrophy type 1: a report of 8 families.

Eight families with lattice corneal dystrophy are reported. The symptoms and signs are almost identical with the typical lattice corneal dystrophy type 1 in western countries. Lattice corneal dystrophy has been considered to be a rare disease until recently, but it might be a more common disorder. This is the first report of a large series of lattice corneal dystrophy in Japan.

Adolescent↗
PubMed1987

Noninvasive measurements of pyridine nucleotide and flavoprotein in the lens.

Abnormalities in glucose metabolism are thought to be among the main causes of cataract formation. The authors have made noninvasive biochemical measurements of the lens that provide information concerning glucose metabolism in the lens epithelium. The autofluorescence of reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) within the rabbit lens were noninvasively measured as a function of depth using redox fluorometry. The peak of the autofluorescence at 440 nm (excited at 360 nm) and 540 nm (excited at 460 nm) were determined at the lens epithelium. When 8 mM sodium pentobarbital, a known inhibitor of mitochondrial respiration, was applied to the lens, the autofluorescence peak at 440 nm increased and that at 540 nm decreased. The 440 nm autofluorescence is thought to be from reduced pyridine nucleotides, whereas the 540 nm autofluorescence is from the oxidized flavoprotein. Blocking lens respiration with pentobarbital caused an increase in the PN/Fp ratio by a factor of 3 within 3.5 hr after pentobarbital application.

Animals↗
PubMed1984

Adenocarcinoma of the ciliary body pigment epithelium in a child.

Tumors arising from the pigment epithelium of the ciliary body are rare and most commonly occur in white adults. We describe a tumor that was clinically indistinguishable from a melanoma or medulloepithelioma occurring in a 7-year-old Japanese boy. Three months after initial evaluation, the eye was enucleated because of intractable intraocular pressure elevation and pain. On pathologic examination the tumor was found to fill approximately one third of the anterior chamber. Light microscopic and ultrastructural findings were consistent with an adenocarcinoma of the ciliary body pigment epithelium. To our knowledge, this is the youngest patient described with this tumor.

Adenocarcinoma↗
PubMedDate not supplied

Combined medical and surgical treatment of severe vernal keratoconjunctivitis.

PURPOSE: We report the efficacy of an alternative method of treatment for vernal keratoconjunctivitis (VKC) that consists of excision of the palpebral conjunctiva followed by supratarsal injection of corticosteroid and five times daily topical application of 0.05% cyclosporine A (CsA) and cromolyn sodium. METHODS: We evaluated 10 patients with severe treat-resistant VKC with corneal complications. The patients were evaluated for symptoms and for signs, including conjunctival changes, corneal limbal infiltrates, vascularization, reduction of epitheliopathy, meibomitis, visual acuity, intraocular pressure, and pathologic evaluation, before and after treatment. RESULTS: All patients showed marked improvement after 2 weeks of treatment. The symptoms (P <.01), signs (P <.02), and the visual acuity of all patients (P <.01) had significantly improved following treatment. Histological examination showed significant inflammatory cell decreases 4 weeks after surgery (P <. 05). CONCLUSION: Surgery plus topical drug therapy may be useful in treating patients with very severe VKC.

Adolescent↗