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Biomedical subjects

K Tsubota

Publications and source records attributed to K Tsubota.

At least 217 records · Page 12Linked to original sources
PubMed1993

Corneal transplantation with donor corneas stored in moist chamber and chondroitin sulfate-containing medium.

Two donor cornea preservation methods, moist chamber and chondroitin sulfate-containing medium, were prospectively compared clinically. Paired corneas from 11 donors were divided into two groups: moist chamber group (mean preservation time 9.1 h) and Optisol (Chiron Co., Irvine, CA, U.S.A.) group (mean preservation time 70.8 h). They were compared in terms of their clinical course, corneal thickness, and endothelial density. Recipient age, sex, and diseases were matched between the groups. Nine of 11 corneas in the moist chamber group, and 10 in the Optisol group remained clear at 6 months after surgery. Decreases of the endothelial density were 28.4% in the moist chamber group, and 30.1% in the Optisol group at 6 months after surgery. No differences were found in either endothelial density or corneal thickness throughout the observation period. It was shown that the corneoscleral preservation using chondroitin sulfate-containing medium was as useful as the conventional moist chamber preservation. Considering the requirement for longer donor preservation time, corneoscleral preservation should be adopted in areas other than the United States.

Adolescent↗
PubMed1993

The effect of aldose reductase inhibitor on the corneal epithelium.

Recent studies of diabetic corneal epitheliopathy have shown that diabetic aphakic patients suffer from an enlarged cell area. This study focuses on a 41-year-old diabetic woman whose mean cell area before treatment was 1,101 +/- 275 microns 2. Seven months after treatment it decreased to 723 +/- 253 microns 2. This case shows that through the application of topical aldose reductase inhibitor, the mean cell area in diabetic aphakic patients can decrease toward a normal number.

Adult↗
PubMed1993

Ocular fatigue is the major symptom of dry eye.

A total of 524 consecutive new patients (195 male, 329 female, 43.4 +/- 20.8 y.o.) were evaluated for the presence of ocular fatigue and/or dry eye. Dry eye was diagnosed based on our criteria, which included symptoms, vital staining, break-up time (BUT) measurement, and the Schirmer test. Among all the patients, 21.2% (111/524) reported symptoms of ocular fatigue and 15.3% (80/524) were diagnosed as having dry eye with symptoms. Of the 111 patients who complained of ocular fatigue, 51.4% (57/111) had dry eye, which was significantly higher than the 15.3% for the entire group (p < 0.001). Additionally, 71.3% (57/80) of dry eye patients with symptoms complained of ocular fatigue, which was also significantly higher than the 21.2% among all patients (p < 0.001). Dry eye patients had a greater number of complaints (4.3 +/- 2.1 per patient) compared to controls (1.9 +/- 1.3 per patient) (p < 0.001). These findings suggest that there is a strong relation between ocular fatigue and dry eye.

Adult↗
PubMed1993

Distribution of autofluorescence in the rabbit corneal epithelium.

Autofluorescence from reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) was measured in order to detect the difference in redox states in rabbit corneal epithelium. The enucleated rabbit eye was mounted in an eye bank eye container with McCarey-Kaufman medium, and the autofluorescence was measured using ocular redox fluorometry as a function of depth. The PN signal distributed evenly whereas the Fp signal was greater in the posterior epithelial region than in the anterior region (p < 0.05). The PN/Fp ratio, a sensitive indicator of tissue redox state, was less in the posterior region. After the application of 1 mM of potassium cyanide in the medium, the ratio increased significantly in each layer (p < 0.001), and the difference between anterior and posterior region diminished. These results indicate that ocular redox fluorometry has the potential to resolve the redox states of the various layers of the corneal epithelium. The posterior region of the epithelium is more active in mitochondrial respiration than the anterior region.

Animals↗
PubMed1993

Aldose reductase inhibition and the phosphorus-31 profile of the intact diabetic rat lens.

Diabetic metabolic change and response to aldose reductase inhibition in the Wistar rat lens were examined with phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectroscopy. To avoid artifacts in sample preparation, we used freshly excised lenses and acquired NMR data for 20 min immediately after lens extraction. The results showed a diabetes-induced time-dependent loss of ATP and phosphorylcholine (PC), an increase in alpha-glycerophosphate (alpha-GP) and inorganic phosphate and the appearance of sorbitol-3-phosphate (S-3-P) and fructose-3-phosphate (F-3-P). Oral but not topical dosing of an aldose reductase inhibitor, 5-(3-ethoxy-4-pentyloxyphenyl)-2,4- thiazolidinedione, resulted in a positive dose-response correlation characterized by a restoration of PC, S-3-P and F-3-P to the prediabetic level; however, alpha-GP and ATP were only partially normalized. The significance of the 31P change was further discussed.

Adenosine Triphosphate↗
PubMed1993

[Corneal endothelium damage by air bag system].

We have reported in the past a car crash in which the air bag system might have caused driver's corneal endothelial cell loss. To evaluate the corneal endothelial cell loss caused by air bag systems, we performed several air bag impact tests. We found that the corneal endothelial cell loss was greater at a distance of 240 mm than other distances. We also found that the corneal endothelial cell loss caused by the air bag which has bigger inflater and heavier material was significantly greater than that caused by other systems. This study offers basic data to improve the safety of air bag systems.

Air Bags↗
PubMed1993

[Histological evaluation of brush cytology of rabbit conjunctiva].

The number of the cells and the layers of the conjunctiva which can be obtained by brush cytology was studied on rabbit conjunctiva using cytological and histological methods. About 1,000, 3,500, and 10,000 conjunctival epithelial cells can be obtained by 7, 14, and 20 brush strokes histological observations showed that all varieties of the layers including basal cells were obtained without destroying the basement membrane. This study showed that the brush cytology can offer single cell suspension only from the conjunctival epithelium, and that brush cytology is useful to investigate the conjunctival epithelium by flow cytometry, polymerase chain reaction, and other methods.

Animals↗
PubMed1992

Corneal epithelial alterations induced by disposable contact lens wear.

PURPOSE: To study the effect of disposable extended-wear soft contact lenses on the corneal epithelium. METHODS: Thirteen healthy patients (1 male, 12 females; average age, 26.3 +/- 7.6 years) with or without histories of previous contact lens use were recruited for this study. Specular microscopic pictures of the corneal epithelium and endothelium were taken with the help of a specular contact lens, before and after 3 months of contact lens use. The pictures were analyzed by means of a computer-assisted morphometric analysis system. RESULTS: The mean cell area and coefficient of variation (CV) of the mean cell area of the corneal epithelium before contact lens use were 639.4 +/- 84.0 microns 2 and 29.1 +/- 13.2, respectively. After lens wear, the mean cell area increased to 819.7 +/- 99.2 microns 2 (P less than 0.01), whereas the CV decreased to 20.0 +/- 6.1 (P less than 0.05). The corresponding values for the endothelium were 300.8 +/- 22.5 microns 2 and 36.4 +/- 7.3 before contact lens use, and remained at 322.3 +/- 27.8 microns 2 and 32.8 +/- 3.7 after contact lens use, respectively (P greater than 0.05). CONCLUSIONS: Based on the 3-month results, disposable extended-wear soft contact lenses caused similar enlargement of the mean cell area of the superficial corneal epithelium, as has been reported previously. It would appear that disposable lenses may cause the same metabolic and physiologic changes in the corneal epithelium as do conventional extended-wear soft contact lenses.

Adult↗
PubMed1992

Specular microscopic observation of normal human corneal epithelium.

The authors analyzed the specular microscopic appearance of normal corneal epithelium, with particular regard to four cell patterns previously identified in pathologic corneas. Corneal epithelia of 75 normal eyes were examined by specular microscopy using a special compound contact lens. There were no elongated or extra large cells, whereas 44.0% and 35.7% of the corneas showed central epithelial nuclei and irregular patterns, respectively. The mean epithelial cell area and corresponding mean coefficient of variation (CV) for each of the corneas were 595.6 +/- 98.8 microns 2 and 30.3 +/- 15.3%, respectively. The values for the endothelium were 325.7 +/- 48.4 microns 2 and 33.6 +/- 6.3%, respectively. Although there was a significant Pearson correlation (r = 0.50, P less than 0.01) between mean endothelial cell area and age, none existed (r = 0.19, P greater than 0.05) between mean epithelial cell area and age, even though there was a relationship (r = 0.35, P less than 0.01) between the mean cell areas themselves. There were no significant relationships among the CV of the epithelium, that of the endothelium, and age. This study presents a powerful new technique and baseline data by which to assess normal corneal epithelium and any aberration.

Adolescent↗
PubMed1992

Metabolic changes in the corneal epithelium resulting from hard contact lens wear.

The metabolic state of rabbit corneas was monitored in vivo using the noninvasive method of corneal redox fluorometry. The autofluorescence signals of reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) were measured in the corneal epithelium with and without contact lens wear. The PN/Fp ratio, which is related to the metabolic status of the tissue, was then calculated for each of these conditions. After application of polymethylmethacrylate (PMMA) contact lenses having an oxygen transmissibility (Dk) of less than 0.1, the PN signal increased and the Fp signal decreased. The PN/Fp ratio, generally a more precise indicator of metabolic state than either of these two quantities alone, was 1.93 +/- 0.78 without contact lenses, and increased to 2.78 +/- 0.86 (p less than 0.0001) with contact lenses. When oxygen-permeable silicon contact lenses (Dk = 12.5) were placed on the corneas, the PN/Fp ratio was found to increase slightly, but not as much as with the PMMA lenses. Newly developed highly oxygen-permeable contact lenses (Dk = 58.8) did not increase this ratio. Our findings indicate that redox fluorometry can be valuable in determining the effects of contact lens wear on corneal metabolism.

Animals↗
PubMed1992

Cytologic evaluation of conjunctival epithelium after cataract surgery.

Although numerous studies have examined corneal epithelial wound healing, few reports describe conjunctival wound healing. Thus, we evaluated the conjunctival epithelium by brush cytology, in which a miniature brush was used to collect many cells relatively noninvasively. The temporal and superior conjunctivae were examined before and after cataract extraction on the first, third, seventh, and fourteenth days and then the first, second, and third months postoperatively, in a group of 20 patients (9 men and 11 women with a mean age of 69 years 3 months +/- 10 years). The cells collected were stained by the Papanicolaou method. Each postoperative specimen contained keratinized, polygonal, round, columnar, elongated, and inflammatory cells, as well as cells with nuclear alterations. No keratinized, elongated, or inflammatory cells were observed preoperatively. In contrast, columnar cells, which were present preoperatively, decreased during the wound healing process. Such nuclear changes as chromatin formation or the appearance of snake-like figures were observed in several patients postoperatively. These cellular changes may represent altered differentiation during the healing process. However, the conjunctival epithelium returned to normal within 2 months postoperatively in all patients.

Aged↗
PubMed1992

Oxiradical-dependent photoemission induced by a phacoemulsification probe.

Oxygen free radical formation by conventional phacoemulsification devices has been postulated as a possible mechanism of corneal endothelial damage during surgery. To test this hypothesis, phacoemulsification probe-induced free radical production was visualized using a single photon-counting camera and an O(2-)-sensitive luciferin derivative, 2-methyl-6-[p-methoxyphenyl-3,7-dihydroimidazo [1,2-a]pyrazin-3-one (MCLA), which allows the visualization of spatial and temporal alterations in free radical production. Within 1 min after starting ultrasound emission, MCLA-dependent chemiluminescence was increased significantly, the intensity of which was maximal at the tip of the probe and tapered along a gradient toward distal portions. The chemiluminescence was suppressed significantly by adding either superoxide dismutase (300 U/ml) or sodium azide (20 mmol/l). By adding deuterium to the medium, MCLA-dependent chemiluminescence significantly increased, suggesting the involvement of singlet oxygen in the reaction.

Azides↗
PubMed1992

Metabolic and morphologic changes in the corneal endothelium. The effects of potassium cyanide, iodoacetamide, and ouabain.

The metabolic pathways of glycolysis and mitochondrial respiration in the corneal endothelial cell are the primary sources of the adenosine triphosphate (ATP) necessary to maintain endothelial structure and pump fluid to maintain the corneal stroma in its normally dehydrated and transparent state. The correlation between endothelial metabolism and morphology in rabbits was studied for 7 days after the application of three different agents: (1) iodoacetamide, used to inhibit ATP synthesis from both glycolysis and respiration; (2) potassium cyanide (KCN), used to inhibit ATP synthesis from respiration only; and (3) ouabain, used to inhibit fluid pumping but not ATP synthesis. After application of each of these three drugs to the corneal endothelium, changes in endothelial morphology were measured. The greatest change resulted from the use of iodoacetamide. Specular microscopic examination of the endothelium after the application of iodoacetamide showed progressive degradation of the integrity of the cellular structure; after 6 hr, there were no discernible cell borders. In those corneas treated with either KCN or ouabain, only minor changes in the endothelium were seen during the full 7 days of the investigation. Computer-assisted morphometric analysis showed an increase in the coefficient of variation of both cell area and perimeter in all cases. This increase was greater in the corneas treated with ouabain than those treated with either iodoacetamide or KCN. Redox fluorometry showed that the metabolic ratio (autofluorescence of reduced pyridine nucleotides divided by that of oxidized flavoproteins) decreased significantly in the iodoacetamide-treated corneas, increased significantly in the KCN group, and showed no significant change in the corneas in the ouabain group, all compared with a control group. The results showed that (1) when ATP produced by both glycolysis and respiration was inhibited by 0.1 mmol/l iodoacetamide, the endothelial cells could not survive, but (2) when ATP synthesis produced by respiration alone was inhibited by 1.0 mmol/l KCN, the cells could survive for at least 1 wk on the ATP produced by anaerobic glycolysis. Furthermore, the polymegathism seen after application of ouabain, a drug that is not believed to affect ATP synthesis but inhibits the endothelial pump function, is greater than that seen as a result of reduced pump function caused by inhibited respiration produced by 1.0 mmol/l KCN. Combining specular microscopy, computer-assisted morphometric analysis, redox fluorometry, and corneal pachymetry allowed correlations between corneal endothelial metabolism, pump function, and morphology to be studied.

Animals↗
PubMed1992

Glycolytic oscillation and effect of metabolic inhibitor on rat lens.

Abnormalities in glucose metabolism are thought to be among the main causes of cataract formation. We have taken noninvasive biochemical measurements of the lens which provides us with information concerning glucose metabolism in the lens epithelium. The autofluorescence of reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) in the rat lens epithelium was measured noninvasively as a function of time using redox fluorometry. The oscillations of the metabolic ratio, PN/Fp, were measured in vivo, in situ, and in the organ-cultured lens. The PN/Fp ratio in the organ-cultured lens ranged from 1.05 to 2.57 within a period of 60-90 minutes (mean +/- SD = 1.52 +/- 0.36). This PN/Fp ratio increased by 23% when a respiratory inhibitor (8 mM KCN) was applied to the lens. However, it decreased by 10% in the presence of a complete metabolic inhibitor (8 mM iodoacetamide). The presence of metabolic oscillations in the in vivo, in situ and cultured lens indicates that this oscillation is a local phenomenon. In cell-free extract systems, oscillations of several intermediates in the glycolytic pathway have been previously demonstrated and this PN/Fp oscillation is thought to be a reflection of glycolytic oscillation.

Animals↗
PubMed1992

Comparison of diagnosis and treatment of Sjögren's syndrome in Japan and United States.

Today, as with western countries, diagnosis and treatment of Sjögren's syndrome (SS) patients in Japan are carried out by a team effort. The clinical manifestations of Japanese SS patients are quite similar also. There are, however, several minor modifications in the diagnosis and treatment of SS patients in Japan, which are presented in this article.

Humans↗
PubMed1992

[Metabolic analysis of the diseased human corneal endothelium].

Redox states of the corneal endothelium in 42 recipient corneas obtained at the penetrating keratoplasty were measured non-invasively using ocular redox fluorometry. Autofluorescence from reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) were measured, and the PN/Fp ratio was used as an indicator of the redox state. Endothelial damage was graded as normal, mildly damaged, moderately damaged, and severely damaged, based on the histopathological findings. Mildly damaged endothelium showed a significantly higher PN/Fp ratio than the that in normal endothelium whereas the ratio was significantly lower in the severely damaged endothelium. These changes in the redox state may represent compensation and decompensation processes of the endothelial metabolism. Ocular redox fluorometry was shown to be useful for the evaluation of the metabolic state in the human corneal endothelium.

Adult↗