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Biomedical subjects

K Tsubota

Publications and source records attributed to K Tsubota.

At least 235 records · Page 13Linked to original sources
PubMed1992

Tear evaporation from the ocular surface.

A simple method was developed to measure tear evaporation. A sensor was inserted into a chamber covering the eye. The humidity inside each chamber then was measured every 10 sec for 2 min with both eyes either closed or open but allowing normal blinking. The difference between these conditions represented evaporation from the ocular surface. Using this method, the tear evaporation rate at 40% ambient humidity (TEROS 40) was calculated. The average TEROS 40 in normal subjects (n = 43) was 15.6 +/- 3.8 x 10(-7) g/sec. It was 9.5 +/- 5.6 x 10(-7) g/sec in patients with dry eye symptoms (n = 72, P less than 0.001). The insertion of lacrimal collagen implants in one group of such patients (n = 10) increased the TEROS 40 from 10.2 +/- 5.5 x 10(-7) g/sec to 18.2 +/- 4.8 x 10(-7) g/sec (P less than 0.01). The instillation of eye drops increased the TEROS 40 significantly in patients with dry eye symptoms for at least 1 min (n = 10, P less than 0.01); a continued effect depended on the type of eye drop. Increased TEROS 40 still was observed 5 min after instillation of viscous eye drops (0.1% and 0.3% sodium hyaluronic acid); the TEROS 40 returned to original levels within 5 min after instillation of artificial tears of normal viscosity with or without 0.05% sodium hyaluronate. In all cases, TEROS 40 returned to original levels within 10 min. This was a quick reliable method for measuring tear evaporation from the ocular surface, and it can be applied to evaluate tear dynamics and subclassifications of dry eyes.

Adult↗
PubMed1992

[Noninvasive metabolic analysis of the diabetic cornea and lens: in vivo measurement].

In vivo measurement of metabolic changes in diabetic cornea and lens were performed using redox fluorometry in nonobese diabetic (NOD) mice. Autofluorescence from reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) were measured, and the PN/Fp ratio was used as a tissue metabolism indicator. The PN/Fp ratios were significantly higher in the diabetic corneal endothelium. Morphometric analysis of the corneal endothelium using specular microscopy revealed no significant differences between the two groups. These results indicate that redox fluorometry is able to detect early metabolic changes in the corneal endothelium and lens epithelium, which are induced by diabetes mellitus. Activation of the polyol pathway may be responsible for the change. Corneal epithelia may be less susceptible to diabetic changes than the corneal endothelium and lens epithelium.

Animals↗
PubMed1991

Specular microscopic observation of human corneal epithelial abnormalities.

The diameter of the cone lens of the specular microscope was enlarged from its original size of 3.5 mm to 6.0 mm. This modification enabled the authors to take clear pictures of the corneal epithelium with a specular microscope (SM) contact lens, because tears could be excluded from the photographic field by exerting even pressure on the cornea. The normal corneal epithelium showed three kinds of cells with no abnormally shaped or reflex cells. As spindle-shaped cells were mainly observed in keratoconus patients, post-penetrating keratoplasty patients, and postepikeratophakia patients, this suggests that these cells may be an indicator of wound healing. Large cells were observed in diabetic aphakic patients, aphakic extended-wear soft contact lens wearers, and aphakic patients using 0.5% indomethacin eye drops; thus, the presence of large cells may indicate suppressed metabolism and mitosis. Colonies of small cells were observed in keratoconjunctivitis patients. Cells with nuclei and irregular cell patterns were observed in all diseased conditions. There are several common abnormal patterns in the corneal epithelium that are observable under the specular microscope. Modified specular microscopic observation can detect these subtle alterations at the cellular level.

Adult↗
PubMed1991

Corneal epithelium following intraepikeratophakia.

The corneal epithelium in eight patients was surveyed by biomicroscopy and specular microscopy before and after the intraepikeratophakia procedure. Autografting of the epithelium was also examined by electron microscopy. Although the superficial layer of the epithelium was damaged, the wing cell layer remained intact, contributing to the epithelialization of the cornea. Epithelialization of the cornea after surgery was completed in three days in all cases. The epithelium was stained with fluorescein, revealing abnormalities in the superficial layer. This stained superficial epithelium was replaced with new epithelium within seven days, but the new, unstained epithelium exhibited an abnormal pattern when observed under the specular microscope. Abnormally shaped cells, cells with nuclei, and white cells were observed, and normal maturation of the epithelial cells was disrupted. These abnormalities lasted more than eight months in three patients. Patient selection and careful follow-up is advised because of the abnormalities of the epithelium.

Adolescent↗
PubMed1991

Efficacy of nine heat and moisture exchangers for intraoperative airway heat conservation.

The performance of heat and moisture exchangers (HMEs) were clinically evaluated for the effectiveness of intraoperative heat conservation. Ten groups of patients were studied, nine groups with commercially available HMEs (Gibeck Humidvent 1, Terumo Brethaid, Portex Thermovent 600, NMI Pneumoist 2, Pall HME15-22, Gambro Engström Edith 1000, Gambro Engström Edith 1500, Gambro Engström Edith Flex and Siemens Servo Humidifier 153) and a control group with no HMEs. Deep temperature of the forehead (107 patients) and heat and humidity at the airway (55 patients) were measured. The temperature decrease in one hour, the total body heat loss, the temperature and absolute humidity of inspired gas and the heat loss from the airway were much better for all groups with HMEs than for the group with no HMEs, and the nine HMEs had different efficiency. There were significant correlations between the index values of body temperature and the index values of heat and humidity at the airway. In conclusion, HMEs were useful devices for preventing heat loss from the airway and maintaining body temperature.

Adult↗
PubMed1991

Corneal epithelium in diabetic patients.

The corneal epithelia of phakic control (n = 13), aphakic control (n = 10), diabetic phakic (n = 10), and diabetic aphakic patients (n = 13) were surveyed under a wide-field specular microscope with a special contact lens. In control patients, the corneal epithelium showed relatively hexagonal cells, which we divided into three groups: bright cells, medium-bright cells, and dark cells. These epithelial cells displayed a smooth-surface configuration. In diabetic phakic patients, the epithelium seemed almost normal, with slightly more irregularity. In diabetic aphakic patients, the epithelium appeared larger. The cells were irregular and easy to distinguish from normal cells. Morphometric analysis showed that the mean cell areas of phakic control, aphakic control, diabetic phakic, and diabetic aphakic patients were 648 +/- 152, 643 +/- 125, 658 +/- 146, and 821 +/- 203 microns 2, respectively. The increase in the average cell area in diabetic aphakic patients was statistically significant. Although no apparent changes of the epithelium could be detected in the diabetic corneal epithelium under biomicroscopy, abnormalities that could be evaluated by specular microscopic images and morphometric analysis were observed.

Aphakia↗
PubMed1991

Detection by brush cytology of mast cells and eosinophils in allergic and vernal conjunctivitis.

The presence of eosinophils in the conjunctival epithelium is indicative of allergies, and detection is currently performed by cotton swab scrapings. Although mast cells are thought to be chemotactic for eosinophils and thus presage their accumulation, the former's use as early indicators of allergy has heretofore been hindered by poor detection methods. The recent development of a special brush now makes it possible to collect many cells with less disturbance of the conjunctival epithelium. In the present study, we have used this brush for conjunctival scraping in 18 patients with vernal and allergic conjunctivitis, and 10 patients serving as controls. The superior and inferior tarsal conjunctiva in both eyes were examined, and the specimens were stained using Hansel's method. Mast cells were observed in at least one of the tarsal conjunctivae in all cases of vernal and allergic conjunctivitis, whereas eosinophils were so observed in only eight cases (44.4%). Neither mast cells nor eosinophils were present in the conjunctivae of the normal group. Although treatment by mast cell stabilizers produced clinical remissions, they induced disappearance of mast cells in only 10 cases (55.6%), whereas in six cases (33.3%) the mast cells increased, and in two cases they were unchanged (11.1%). Six cases (33.3%) each showed disappearance of, increase in, and no change in eosinophils, reflecting even less of a response of these allergic cells to the treatment. The presence of mast cells and eosinophils, as determined by our cytologic method, was found to be correlated with the early detection, but not the clinical severity, of allergic conjunctivitis.

Adolescent↗
PubMed1991

Cytological evaluation of adenoviral follicular conjunctivitis by cytobrush.

Conjunctival brush samples from 38 patients with acute conjunctivitis were examined to determine whether cellular features could be utilized for cytodiagnosis. Of all cases, 32 (84%) patients showed a characteristic cell pattern for adenoviral follicular conjunctivitis (AFC) and in the remaining 6 (16%) patients herpetic infection was suggested cytologically. The background of the conjunctival smears from patients with AFC was characterized by the predominance of lymphocytes with little fibrinous discharge. In addition, two types of nuclear alterations were demonstrated i.e. intranuclear inclusions and a so-called ground-glass nuclear appearance. Ground-glass nuclei occurred more frequently than intranuclear inclusions in patients with AFC. However, the presence of lymphocytes in conjunctival smears was a useful criterion for making the differential diagnosis between herpetic and adenoviral infections. Thus, in the absence of these three cellular changes, i.e. ground-glass nuclei, intranuclear inclusions and lymphocytic background, infectious conditions other than AFC may be considered, regardless of the numbers of conjunctival cells present. Emphasis is placed on the value of conjunctival brush cytology for the rapid diagnosis of cases of suspected AFC.

Adenovirus Infections, Human↗
PubMed1990

Metabolic studies of galactosemic cataract.

Experimental diabetic and galactosemic animal models are widely used to study diabetes-induced complications. Galactose feeding can rapidly produce cataract, retinopathy and nephropathy; it is therefore favored over the diabetic model. Although the common feature for both models is the activation of aldose reductase, there are substantial differences between the two--not only does the rate of cataract progression differ but the metabolic patterns are far more complex than for polyol production alone. We here present the result of a comparison between diabetic and galactosemic lenses and show the differences in phosphorus and aldose metabolism, cell integrity and osmotic environment.

Animals↗
PubMed1990

Image analysis of the corneal epithelium.

The method for quantifying corneal epithelial images has been examined. When pictures were developed, the images were stored in the memory of the image processing system by video camera. The distribution of the density of the images was analyzed. The density of each pixel of an image was assigned one of 256 grades, from completely black to completely bright. The average (AV), the standard deviation (SD), the coefficient of variation (CV), the skewness (SK) and the sharpness (S) of the density were calculated. Normal epithelium could be differentiated from abnormal by subjectively observing the shapes of the cells, the sizes of the cells and the irregularity of the cell pattern. But there were no statistical differences between the two groups with regard to the AV, SD, CV, SK and S of normal (n = 4) and abnormal (n = 8) corneal epithelial images. Simple analysis of density distribution could not be used as a parameter for the evaluation of the cells.

Aphakia↗
PubMed1990

Application of erbium: YAG laser in ocular ablation.

Recent developments in lasers have provided us the possibility of laser ocular surgery. The xenon, argon, neodymium:YAG and dye lasers have been successfully used in out-patient clinics. The excimer laser has been attracting researchers' interest in the new application of laser to cornea and lens. The erbium:YAG laser emits a 2.94-microns beam that can ablate the transparent ocular tissues such as lenses and corneas. The author has applied this laser to the cornea, lens, vitreous and other ocular tissues. The erbium:YAG laser beam was directed through a 1.5-meter-long, 200-microns-diameter fiberoptic guide. The radiant energy measured about 50 mJ at the end of the probe. The laser was emitted as a 400-microsecond pulse. Freshly enucleated rabbit eyes were used in this study. Laser burns were applied to the tissue surface at various energy settings. At minimal power, the tissues were coagulated by the erbium:YAG laser application. At a power of more than 636-954 mJ/mm2, tissue began to evaporate; the tissue loss was observed under a surgical light microscope. Corneal photoablation, lens ablation, iridotomy, trabeculotomy, cutting of the vitreous and retinal ablation were easily performed. Like the excimer laser, the erbium:YAG laser is a potential tool for ocular surgery.

Animals↗
PubMed1990

[Brush cytology for the evaluation of dry-eye].

A special brush was developed for collection of conjunctival cells with better integrity of the harvested specimens. Using this brush, cells were collected from temporal bulbar conjunctiva of 20 normal eyes and 40 eyes with dry-eye, and were stained by the modified Papanicolau method, Keratinized cells (K) and goblet cells (G) were classified into 5 categories, from (-) to ( ) according to the numbers of the cells observed. Normal eyes were categorized as K (-):16, K(+/-):4, G (+):2, G(++):18, Eyes with dry-eye were K (-):3, K (+/-):8, K (+) 13, K (++):11, K ( ):5, and G (-):7, G (+/-):7, G (+):22, G (++):4. Clinical severity and the rose Bengal score corresponded to these categories. This technique can detect cytological changes in conjunctival cells in terms of shape and quality of staining. Eyes with dry-eye could be evaluated in relation to the numbers of keratinized cells and goblet cells.

Adult↗
PubMed1990

[Measurement of tear evaporation from ocular surface].

A new method for measuring tear evaporation from the ocular surface is developed. The change of humidity in the closed chamber around the eye was recorded, with eyes open and eyes closed. Theoretical equations were used for data analysis, and the evaporation coefficient K, the tear evaporation volume at the environmental humidity of 40% were calculated. We examined 28 normal eyes and 58 eyes of dry eye patients. Evaporation coefficient K (x 10(-4)/sec) were 32.4 +/- 9.2 in normal and 16.5 +/- 11.3 in dry eyes (p less than 0.001). Tear evaporation volume at the environmental humidity of 40% (x 10(-7) g/sec.eye) were 16.2 +/- 4.7 in normal and 8.4 +/- 5.7 in dry eyes (p less than 0.001). This method is so simple and non-invasive that it could be used as a new examination for dry eye.

Adolescent↗
PubMed1989

Lens redox fluorometry: pyridine nucleotide fluorescence and analysis of diabetic lens.

We performed both ex vivo and in vivo fluorometric analyses of pyridine nucleotides (PN) in rabbit and rat lenses. Rabbit lens PN fluorescence (99% NADH) was found to have an excitation maximum at 366 nm and an emission maximum at 462 nm (366:462). The only other fluorescent chromophore in that region of the spectrum has excitation and emission peaks at 328 and 460 nm, respectively. Anaerobic glycolysis in the lens was stimulated by KCN, a known inhibitor of mitochondrial respiration, after which a time-study of fluorescence intensities was performed. Over the course of a 3.5 hr period following treatment with KCN, the PN signal showed a statistically significant increase relative to that in the control lenses (those treated with KCl). while the 328:460 signal (which may be due to some protein involved in energy transfer with the PN) had a significantly greater decrease. We also found that fluorescence intensity of NADH in solution is linearly proportional to physiologic-range concentration. Moreover, there was a close correlation between fluorescence intensity of rat lens PN as measured on a specular microscope-coupled redox fluorometer capable of in vivo use, and the lens PN levels as determined by the analytical cycling assay technique. This fluorometer was then employed to assess the redox state in rats with streptozotocin-induced diabetes. The normalized ratio of PN to flavoproteins (Fp) in the lens epithelium increased from 0.96 +/- 0.12 in the normal state to 1.48 +/- 0.30 2 weeks after diabetes induction. In contrast, the ratio in the diabetic lens treated with an aldose reductase inhibitor, sorbinil, did not increase. The increase in the PN:Fp ratio therefore reflects activation of the polyol pathway and its associated metabolic activities, which results in an increase in the NADH:NAD ratio in the diabetic rat lenses. Our results indicate that the non-invasive, real-time method of redox fluorometry may be useful in the early detection and evaluation of cataracts and other disorders in lens metabolism, long before opacities occur. It can be used to monitor the disease process and evaluate the efficacy of such drugs as aldose reductase inhibitors on a biochemical level.

Animals↗
PubMed1989

Hard contact lens-induced metabolic changes in rabbit corneas.

The biochemistry of contact lens-cornea interaction is not well understood, although previous studies have suggested that corneal metabolic changes may be the underlying factor in morphological alterations. Using a rabbit model, this interaction has been examined with 31P nuclear magnetic resonance (NMR) spectroscopy, which detects signals principally from the epithelium. The examination was supplemented with electron microscopy and histochemistry. Polymethylmethacrylate lenses caused reversible changes, including activation of anaerobic glycolysis and disturbance of membrane metabolite levels. These changes were far more severe than those occurring during prolonged eye closure. There appears to be an association between cellular deterioration and loss of membrane metabolites. On the other hand, oxygen-permeable silicone lenses allowed maintenance of nearly normal metabolic patterns. These results show multifaceted corneal response to hard contact lens wear.

Animals↗