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Biomedical subjects

M Ohji

Publications and source records attributed to M Ohji.

At least 55 records · Page 3Linked to original sources
PubMed1997

The double-mirror gonioscopic lens for surgery of the anterior chamber angle.

Intraoperative examination of the anterior chamber angle is necessary during several glaucoma procedures, including goniosynechialysis and goniotomy. Many of the available lenses for this purpose are difficult to use because they require oblique illumination and their size interferes with surgical manipulations at the limbus. We have developed a double-mirror gonioscopic lens that uses direct illumination; provides an upright image of angle structures; and has a small diameter, allowing simultaneous access to the entire limbal region. We compared our lens with the Posner goniomirror (Ocular Instruments, Bellvue, Wash) and found that it provides an equal view of angle structures. The double-mirror gonioscopic lens facilitates the intraoperative visualization of the anterior chamber angle and should allow surgeons who treat glaucoma to more accurately and safely perform angle-related procedures.

Animals↗
PubMed1997

Horizontal transposition of vertical rectus muscles for treatment of excyclotropia.

BACKGROUND: Horizontal transposition of the vertical rectus muscles has been performed for treatment of excyclotropia associated with congenital absence of the superior oblique, and for residual excyclotropia after the Harada-Ito operation. However, the amount of excyclotropia that can be corrected and whether this technique alters the vertical muscle balance is not well known. We report the surgical results of three patients with pure excyclotropia who underwent unilateral one-half tendon width horizontal transpositions of vertical rectus muscles. METHODS: A one-half muscle width temporal transposition of the superior rectus and nasal transposition of the inferior rectus muscles of one eye was performed in three patients with pure excyclotropia and no associated hypertropia. All three had intermittent torsional diplopia before surgery. RESULTS: Postoperatively, excyclotropia decreased significantly in all fields of gaze, with 8 degrees of reduction by synoptophore and 12.3 degrees of reduction by fundus photography on average. There was no associated vertical or horizontal deviation. All three patients reported improvements of cyclofusion. CONCLUSION: One-half muscle width temporal transposition of the superior rectus and nasal transposition of the inferior rectus muscles was effective in ameliorating excyclotropia and corrected subjective complaints without altering vertical muscle balance.

Adult↗
PubMed1997

Diamond-dusted silicone cannula for epiretinal membrane separation during vitreous surgery.

PURPOSE: To report a diamond-dusted silicone cannula as a tool for membrane separation during vitreous surgery. METHODS: A diamond-dusted silicone cannula was fashioned from flexible silicone tubing with a beveled tip and coated with diamond fragments for use during vitreous surgery. RESULTS: The instrument was used successfully in seven eyes with idiopathic macular hole and was found to be particularly useful for removing residual vitreous cortex and epiretinal membranes from around the hole. It was also effective in removing "immature membranes" in three eyes with proliferative vitreoretinopathy. CONCLUSION: The diamond-dusted silicone cannula is a useful tool for removing thin epiretinal membranes and vitreous cortex that may be difficult or nearly impossible to remove safely using other techniques.

Catheterization↗
PubMed1997

Sulfur hexafluoride and perfluoropropane do not escape from a plastic syringe closed with a stopcock.

PURPOSE: To evaluate during various intervals of time the escape of long-acting gases contained in a plastic syringe closed with a stopcock or a plastic cap. METHODS: A 60-ml plastic syringe was filled or partially filled with a long-acting gas, either sulfur hexafluoride or perfluoropropane. The tip of the syringe was closed with either a stopcock or the syringe's plastic cap. After various intervals of time, the concentration of the long-acting gas in the syringe was measured by gas chromatography. RESULTS: The concentration of both long-acting gases was higher than 98% at 24 hours after filling when the syringe was closed with a stopcock; however, it was less than 41% when the syringe was filled and capped tightly with its plastic cap. CONCLUSION: The proportion of long-acting gases escaping in 24 hours from a filled syringe capped with a stopcock is clinically insignificant.

Chromatography, Gas↗
PubMed1997

Differentiating full thickness macular holes from impending macular holes and macular pseudoholes.

AIMS: The reliability of scanning laser ophthalmoscope (SLO) microperimetry in differentiating full thickness macular holes from macular pseudoholes and impending macular holes was evaluated. METHODS: 106 eyes with the clinical diagnosis of full thickness macular holes, macular pseudoholes, and impending (stage 1) macular holes were examined for the presence of deep or relative scotoma using SLO microperimetry. The relation between these scotomas and the clinical diagnosis was studied. RESULTS: Deep and relative scotomas were detected in all 57 eyes with clinically defined full thickness macular holes. In contrast, among 49 eyes diagnosed with macular pseudoholes or impending macular holes, no deep and only one relative scotoma was observed. The sensitivity of the presence of a deep scotoma as an indicator of the clinical diagnosis of a full thickness macular hole was 100% (57 of 57), and the specificity was 100% (49 of 49). The sensitivity of the presence of a relative scotoma was 100% (57 of 57) and the specificity was 98.0% (48 of 49). CONCLUSION: With SLO microperimetry, full thickness macular holes can be precisely and objectively distinguished from other conditions that mimic macular holes.

Adult↗
PubMed1997

An applicator-shaped scleral depressor for vitreoretinal surgery.

This article describes an instrument that combines a standard T-shaped scleral depressor at one end with a cotton applicator-shaped depressor at the other end. The applicator-shaped depressor has a matted surface to prevent slippage. This simple instrument has several advantages over depressors now available for intraoperative use.

Eye Diseases↗
PubMed1997

Subretinal fluid drainage with the erbium:YAG laser in rabbit eyes.

BACKGROUND AND OBJECTIVE: To evaluate the efficacy and safety of the erbium:yttrium-aluminum-garnet (Er:YAG) laser for choroidotomy as a means of performing external drainage of subretinal fluid with less risk of choroidal bleeding. MATERIALS AND METHODS: The authors tested this application in a rabbit model of retinal detachment by evaluating the effects of Er:YAG laser energy on the bare choroid at various energy settings (1, 2, 3, or 5 mJ/pulse) and repetition rates (2, 4, 10, or 30 Hz). RESULTS: Although the choroid was not perforated at low energy and frequency settings, choroidotomy was successfully achieved as energy and repetition rate were increased. Through higher energy levels per pulse and higher repetition rates, choroidotomy was achieved at lower total energy levels. No retinal damage was detected after laser choroidotomy. Choroidal bleeding was noted in 2 of 97 eyes; however, no subretinal hemorrhage occurred. CONCLUSION: These results indicate that the Er:YAG laser may be a clinically useful tool for retinal reattachment surgery.

Animals↗
PubMed1996

Cytokine effects on phagocytosis of rod outer segments by retinal pigment epithelial cells of normal and dystrophic rats.

PURPOSE: Phagocytosis of rod outer segments (ROS) is an important function of retinal pigment epithelial (RPE) cells. Since the details of the process are not fully known, we studied effects of cytokines produced by RPE and photoreceptor cells on phagocytosis of ROS by rat RPE cells. METHODS: RPE cells were isolated and cultivated from two strains of rats: Sprague-Dawley (SD) rats with normal phagocytosis and Royal College of Surgeons (RCS) rats, which have genetic deficiencies in ROS phagocytosis. A double immunofluorescence staining technique was used to study the effects in vitro of several cytokines on phagocytosis of ROS. RESULTS: We found that transforming growth factor beta-1 (TGF-beta 1) had dose-dependent effects on RPE cells of both strains of rat: at a concentration of 10 ng/ml, TGF-beta 1 significantly (p < 0.01) reduced total ROS (to 74% of control in SD rats and to 51% of control in RCS rats), reduced bound ROS (to 56% of control in SD rats and to 48% in RCS rats), and increased the ratio of ingested ROS to total ROS (to 140% in SD rats but not significantly in RCS rats). Treatment of medium with anti-TGF-beta 1 antibody before incubation of RPE cells of SD rats with TGF-beta 1 decreased the magnitude of these effects. The cytokine acidic fibroblast growth factor (aFGF, 10 ng/ml) affected RPE cells of SD rats only, decreasing ROS ingested to 56% of control and the ratio of ingested ROS to total ROS to 64% of control. We also examined effects of basic fibroblast growth factor and insulin-like growth factor. None of the cytokines tested increased ingestion of ROS by RPE cells of RCS rats. CONCLUSIONS: Our results suggest that TGF-beta 1 and aFGF have roles in regulating ROS phagocytosis by normal and dystrophic RPE cells in the rat.

Animals↗
PubMed1996

A new wound healing model of retinal pigment epithelial cells in sheet culture.

PURPOSE: To evaluate some RPE cell functions, such as wound healing, in a preparation more similar to in situ conditions, we developed a method to obtain and culture retinal pigment epithelial (RPE) cells as a sheet. And we assessed the effects of fetal bovine serum (FBS) on the rate of RPE wound healing. METHODS: We prepared RPE sheet cultures by incubating rat eyes in 0.1% proteinase K for 13 min, peeling away the neural retina-RPE complex, and then incubating the tissue for 1 h to promote spontaneous separation of the RPE sheet from the retina. After several days of incubation, the cultured sheets of RPE cells were examined by phase-contrast microscopy, scanning and transmission electron microscopy and immunocytochemistry. We made round defects 1 mm in diameter in cultured RPE sheets and estimated the rate of wound closure in media with different concentrations of FBS (0 to 10%). RESULTS: The RPE cells cultured in sheets retained their in situ features, including microvilli, tight junctions and gap junctions, and the distribution of actin and cytokeratin filaments. A wound was noted to close with restoration of a polygonal configuration. The rate of wound closure depended on serum concentration in the culture medium; when supplemented with 10% fetal bovine serum, wound closure was complete in approximately 40 h. CONCLUSIONS: The RPE sheet-culture technique we developed thus provides a suitable model for studying such RPE cell functions as wound healing or phagocytosis.

Animals↗
PubMed1996

A technique for contact lens fixation during vitreous surgery.

The authors describe a technique for contact lens fixation during vitreous surgery. A contact lens support ring was designed that requires only a single suture for fixation and provides improved stability and centering of a sutured fundus contact lens. These features save time and allow concentration on the surgical goals rather than on the contact lens.

Contact Lenses↗
PubMed1995

Membrane delaminating wedge.

Iatrogenic retinal tears may complicate procedures to treat proliferative vitreoretinal diseases. To decrease the risk of this complication, we developed a new instrument, the membrane delamination wedge, that allows the surgeon to separate the proliferative membranes from the retina effectively and safely.

Diabetic Retinopathy↗
PubMed1995

Double-mirror peripheral vitrectomy lens.

Many surgeons use prism lenses to see the periphery of the fundus during vitrectomy; however, chromatic aberrations in higher-power prismatic lenses cause blurring of the peripheral image. For better visualization of the periphery of the fundus, we developed a new contact lens, the double-mirror peripheral vitrectomy lens. The new lens is a quartz cylinder with two mirrors, and it provides a crisp, clear, upright image of much more of the peripheral fundus than is visible through conventional prism lenses. The new lens also provides a wider area of view than conventional prism lenses.

Eye Diseases↗
PubMed1995

Characterization of immortalized rabbit corneal epithelial cells with SV40 large T antigen.

The authors developed a line of immortalized rabbit corneal epithelial cells by transfecting a primary culture of New Zealand White (NZW) rabbit corneal epithelial cells with Simian virus 40 (SV40) T antigen gene using a calcium phosphate precipitation method. The transfected cells, which survived more than 40 passages and 400 population doublings, showed some ability to form colonies in soft agar, and had doubling times and plating efficiencies not significantly different from those of untransfected cells. The epithelial nature of the transfected cells was confirmed by immunofluorescence staining with the antibody to 64 kD keratin (AE5), a specific marker for corneal type epithelial cells. Immunofluorescence microscopic examination revealed that the transfected cells expressed major basement membrane components of epithelial cells, including collagen types IV and VII and laminin. Electron microscopic studies demonstrated the presence of microvilli and intercellular in cultured transfected cells. These results indicate that the transfected cells retain some of the normal phenotypic characteristics of corneal epithelial cells and may therefore be used to study the corneal epithelium in vitro.

Animals↗
PubMed1994

Basement membrane synthesis by human corneal epithelial cells in vitro.

PURPOSE: Collagen gels may prove to be potential carriers for transplantation of cultured corneal epithelial cells. The purpose of this study was to evaluate the suitability of collagen gels in comparison with corneal stromal blocks as the substrate to support the growth of human corneal epithelial cells in culture and the synthesis and deposition of the basement membrane components by these cells. METHODS: Corneal epithelial sheets, freed from the culture dishes using Dispase II (Boehringer Mannheim, Indianapolis, IN), were cultured on corneal stromal blocks. Deposition of laminin, type IV collagen, type VII collagen, and perlecan (heparan sulfate proteoglycan) were evaluated immunohistochemically after 4 days, 7 days, 2 weeks, and 3 weeks. Human limbal explant cultures were established on collagen gels prepared from bovine type I collagen with or without addition of cultured human corneal fibroblasts. After 1, 2, 3, and 4 weeks, the deposition of the basement membrane components was evaluated immunohistochemically. RESULTS: Corneal epithelial cells, cultured on corneal stromal blocks as well as on collagen gels with or without fibroblasts, deposited laminin, type IV collagen, perlecan, and type VII collagen at the interface of the cells and the substrates. However, different substrates differentially influenced the temporal pattern of the deposition of various basement membrane components. On the stromal blocks, deposition of laminin, type IV collagen, and perlecan by the epithelial cells was evident at 1 week. Type VII collagen was detected at 2 weeks. On the collagen gels with fibroblasts, deposition of laminin, type IV collagen and perlecan was detectable at 1 week. In the epithelial cultures on the collagen gels without fibroblasts, only perlecan was detectable at 1 week. At 2 weeks, all of the basement membrane components, including type VII collagen were detectable on the collagen gels, either with or without fibroblasts. CONCLUSION: Human corneal epithelium cultured on collagen gels or on corneal stromal blocks can synthesize and deposit basement membrane components, including laminin, type IV collagen, type VII collagen, and perlecan within 2 weeks in culture. Therefore, collagen gels may serve as potential carriers for human corneal epithelial transplantation.

Aged↗
PubMed1993

Conjunctival epithelial cell hypermitosis and goblet cell hyperplasia in atopic keratoconjunctivitis.

Atopic diseases that include eczema (atopic dermatitis), asthma, and seasonal and perennial rhinoconjunctivitis are common manifestations of abnormal immediate hypersensitivity. Ocular involvement, such as atopic keratoconjunctivitis, characteristically includes conjunctival and corneal inflammation, and in a severe form, conjunctival scarring, symblepharon, corneal epitheliopathy, and visual loss. To examine the conjunctival cellular abnormalities in atopic keratoconjunctivitis, we studied the in vivo differentiation and tissue-culture growth characteristics of conjunctiva from normal subjects and patients with severe atopic keratoconjunctivitis. We examined conjunctival biopsy specimens to determine epithelial mitotic rate and goblet cell frequency, and we studied conjunctival explants to determine the latent period for fibroblast outgrowth and fibroblast doubling time. The mitotic rate for atopic keratoconjunctivitis, 6.7% +/- 2.1% (11 patients), was statistically significantly greater than for normal subjects, 2.0% +/- 0.63% (seven subjects) (P = .05). Also the goblet cell frequency for atopic keratoconjunctivitis, 14.6% +/- 3.4% (11 patients), was statistically significantly greater than for normal subjects, 4.8% +/- 0.92% (seven subjects) (P = .02). The latent period for fibroblast outgrowth and the fibroblast doubling time for atopic keratoconjunctivitis were not statistically significantly different from normal control subjects. Therefore, atopic keratoconjunctivitis was associated with conjunctival epithelial hypermitosis, goblet cell hyperplasia, and normal fibroblast tissue-culture growth. These characteristics may be useful in the diagnosis of atopic keratoconjunctivitis. We previously studied another disease characterized by chronic conjunctival inflammation and scarring, cicatricial pemphigoid, which also demonstrated conjunctival epithelial hypermitosis, but in contrast there was near absence of goblet cells, and the fibroblasts were hyperproliferative. These differences may be used to distinguish atopic keratoconjunctivitis from cicatricial pemphigoid.

Aged↗
PubMed1993

Transforming growth factor-beta stimulates collagen and fibronectin synthesis by human corneal stromal fibroblasts in vitro.

The effects of transforming growth factor-beta (TGF beta) and epidermal growth factor (EGF) on the synthesis of collagen and fibronectin, and on the proliferation of human corneal stromal fibroblasts in vitro, were evaluated. Human corneal stromal fibroblasts in culture were incubated for 48 hours with TGF beta or EGF in the absence of serum. Collagen and fibronectin in the culture media were measured by a collagenase-digestion assay and a competitive ELISA, respectively. The effects of the growth factors on proliferation were assessed by 3H-thymidine incorporation. Collagen synthesis was dose-dependently stimulated by TGF beta; at a concentration of 1 ng/ml of TGF beta, a 120% increase in collagen synthesis was seen over that of controls (p < 0.01). EGF, at a concentration of 10 ng/ml, induced a 40% increase in collagen synthesis over that of controls (p < 0.01). The maximum stimulation by TGF beta was greater than that by EGF (p < 0.05). Fibronectin synthesis was stimulated by TGF beta and EGF in a dose-dependent manner; 230% (p < 0.001) and 210% (p < 0.01) increases in fibronectin synthesis were caused by 10 ng/ml TGF beta and EGF, respectively. TGF beta and EGF dose-dependently stimulated 3H-thymidine incorporation. The maximum increases in 3H-thymidine incorporation reached 180% (p < 0.001) and 190% (p < 0.001) over that in controls, at 10 ng/ml concentrations of TGF beta and EGF, respectively. In conclusion, both TGF beta and EGF are potent stimulants of collagen and fibronectin synthesis and proliferation. Therefore, these two growth factors may be effective alternatives or additional choices for the treatment of corneal ulcer.

Cell Division↗
PubMed1993

Corneal epithelial cell attachment with endogenous laminin and fibronectin.

PURPOSE: To evaluate the role of endogenously produced laminin and fibronectin as well as the effect of exogenous laminin and fibronectin in the attachment of human corneal epithelial cells in vitro. METHODS: Primary cultured human corneal epithelial cells labeled with 3H-thymidine were seeded onto plates coated with laminin or fibronectin, or onto uncoated bacteriologic plates. Attachment of cells was measured in the presence or absence of antisera against laminin or fibronectin, by counting radioactivity. RESULTS: Human corneal epithelial cells attached to plates coated with human laminin or human fibronectin in a dose-dependent manner, with 69% and 50% of cells attached to the wells coated with 40 micrograms/ml of laminin and fibronectin, respectively (P < 0.001). The percentage of attachment to uncoated bacteriologic plates increased from 1.2% at 45 min of incubation to 6.7% at 90 min, 22.2% at 3 hr, and 40.1% at 6 hr of incubation. Cycloheximide, a protein synthesis inhibitor, completely inhibited cell attachment. Rabbit antiserum against human fibronectin reduced cell attachment to the uncoated plates to 67% of the control value (P < 0.01), whereas rabbit antiserum against human laminin decreased the attachment to 52% of the control (P < 0.01). A combination of these two antisera reduced cell attachment to 46% of the control (P < 0.01). CONCLUSIONS: Endogenous laminin and fibronectin as well as exogenous laminin and fibronectin play significant roles in the attachment of human corneal epithelial cells in culture.

Autoradiography↗