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Biomedical subjects

C K Joo

Publications and source records attributed to C K Joo.

At least 37 records · Page 2Linked to original sources
PubMed1999

Horizontal cells of the rat retina are resistant to degenerative processes induced by ischemia-reperfusion.

The fate of calbindin D28k (calbindin)-labeled horizontal cells in the ischemic rat retina induced by increasing intraocular pressure was investigated by immunocytochemistry using an antiserum against calbindin. In the normal retina, strong calbindin-like immunoreactivity was seen in the horizontal cells, and the density of the labelled horizontal cells was 815.3+/-15.2 per mm2. The thickness of the treated retina became progressively thinner with increasing reperfusion time after the ischemic insult due to a loss of retinal cells in the inner and outer nuclear layers. However, the densities of the horizontal cells per mm2 were 814.0+/-26.4 at 1 week, 813.3+/-20.8 at 2 weeks, and 812.6+/-11.5 at 4 weeks, indicating that horizontal cells did not degenerate during experimental periods. Thus, calbindin may have a protective role for horizontal cells to ischemic insult by its ability to buffer calcium influx in the rat retina.

Albinism↗
PubMed1999

Degeneration and transdifferentiation of human lens epithelial cells in nuclear and anterior polar cataracts.

PURPOSE: To study the possible mechanisms of cataractogenesis by evaluating the characteristics of cataractous lens epithelial cells (LECs) in different types of human cataract. SETTING: Kangnam St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea. METHODS: Lens epithelial cells attached to the anterior capsules in eyes with nuclear or anterior subcapsular were analyzed for morphological characteristics by electron microscopy and for cellular characteristics by immunohistochemistry. RESULTS: Human LECs beneath the anterior capsule were degenerated in nuclear cataracts and were transdifferentiated in anterior polar cataracts. In senile nuclear cataractous lenses, LECs beneath the anterior capsule showed degenerative changes in morphology. In nuclear cataracts, LECs were immunohistochemically positive for cytokeratin and vimentin, while those in anterior polar cataracts were positive for vimentin only. The LECs of anterior subcapsular cataracts were transdifferentiated into spindle-shaped fibroblast-like cells without cellular junctions and embedded within a fibrillar meshwork mass. The extracellular matrixes in the anterior capsule of anterior subcapsular cataracts were immunohistochemically positive for fibronectin, laminin, collagen type I, and collagen type IV. CONCLUSIONS: Lens epithelial cells in different types of cataracts have distinct cellular characteristics and may possess a bipotential nature with the ability to transdifferentiate into mesenchymal cells. This may be an underlying mechanism for the development of cataract and capsule opacification.

Adult↗
PubMed1999

Corneal perforation during laser in situ keratomileusis.

Two cases of corneal perforation that occurred during laser ablation but not during flap formation in laser in situ keratomileusis (LASIK) are reported. In the first case, no problem in flap formation occurred, and stromal bed thickness was assumed to be about 239 microns after laser application. However, a stromal bed perforation was found when 608 pulses were applied (theoretical ablation depth was 140 microns). Excessive dehydration due to prolonged exposure to the operating microscope light may change the ablation rate and cause corneal perforation. In the second case, LASIK retreatment was performed using the original flap for correction of regressed myopia (-4.0 diopters). Although the stromal bed thickness was assumed to be about 175 microns after the laser application, a stromal bed perforation was found when 151 pulses were applied (theoretical ablation depth was 37 microns). Unexpected corneal ectasia after the first LASIK treatment may cause a corneal perforation in LASIK retreatment. In conclusion, excessive dehydration of the cornea should be avoided, and careful examination of the corneal shape is necessary to prevent corneal perforation during laser ablation in LASIK.

Adult↗
PubMed1999

Corneal flap thickness in laser in situ keratomileusis using an SCMD manual microkeratome.

PURPOSE: To evaluate corneal flap thickness in laser in situ keratomileusis (LASIK) and to measure variables correlated with corneal flap thickness. SETTING: Kangnam St. Mary's Hospital, Department of Ophthalmology, College of Medicine, The Catholic University of Korea, Seoul, Korea. METHODS: This prospective study comprised 69 eyes of 66 patients having LASIK with the VISX Star laser and SCMD manual microkeratome. Corneal thickness, keratometry, and refractive error were measured preoperatively, the time taken to complete the corneal flap and its thickness were recorded intraoperatively, and visual outcome was followed postoperatively. Corneal flap thickness was calculated as the thickness of the corneal stromal bed subtracted from the total corneal thickness. RESULTS: Mean corneal flap thickness was 137.18 microns +/- 33.66 (SD). The thickness in 32 eyes (46.4%) was less than 135 microns, in 17 eyes (24.6%) from 135 to 165 microns, and in 20 eyes (29.0%) greater than 165 microns. There was no relationship between corneal flap thickness and degree of myopia, steepening of cornea, or time taken to complete the flap. However, the thickness of the corneal flap increased with the thickness of the cornea. Visual outcome was slightly better in the group with thick corneal flaps than in the one with thin corneal flaps, although the difference was not statistically significant. CONCLUSION: Corneal flap thickness was variable in LASIK using the SCMD microkeratome. There was a correlation between corneal flap thickness and preoperative corneal thickness.

Adult↗
PubMed1999

Effect of resection velocity and suction ring on corneal flap formation in laser in situ keratomileusis.

PURPOSE: To determine the effects of microkeratome-cutting velocities and the suction ring on corneal flap creation. SETTING: Department of Ophthalmology, College of Medicine, The Catholic University of Korea, Seoul, Korea. METHODS: Procedures were performed under clinical settings in 65 pig eyes. Keratometric diopters (D) were measured before and after application of the suction ring. Corneal thickness was measured before and after resection cutting, and the difference was taken as flap thickness. The microkeratome was initially set at a resection thickness of 160 microns. The blade oscillation (turbine velocity) was set at 30, 35, and 42 psi. The translational velocity was arbitrarily divided into high (1 to 2 seconds), moderate (3 to 5 seconds), and low (6 seconds or more). Data were analyzed by varying the velocities consecutively. Photographs of the cut surface were acquired by scanning electron microscopy to evaluate resection morphology by comparison. RESULTS: Mean refractive powers were 39.94 D +/- 0.66 (SD) and 39.69 +/- 0.98 D before and after application of the suction ring, respectively; however, no significant difference was observed (P = .216). Lower surgeon translational velocity resulted in a significantly thicker corneal flap in 8 of the 9 paired comparisons (P < .05). Higher turbine velocity resulted in a significantly thicker corneal flap in 7 of the 9 paired comparisons (P < .05). The cut surface was smoother at higher turbine and lower translational velocity. The initial cut margin was steeper at higher translational velocity. CONCLUSIONS: The increase in intraocular pressure induced by the suction ring had no significant effect on keratometric power. At higher turbine and lower translational velocities, the corneal flap was thicker and the cut surface smoother. Higher translational velocities made the initial cut margin steeper.

Animals↗
PubMed1999

Posterior capsule opacification in eyes with a silicone or poly(methyl methacrylate) intraocular lens.

PURPOSE: To evaluate the effect of poly(methyl methacrylate) (PMMA) and silicone intraocular lenses (IOLs) on posterior capsule opacification (PCO) after cataract surgery. SETTING: Kangnam St. Mary's Hospital, Seoul, Korea. METHODS: This retrospective study comprised 48 patients (54 eyes) who had neodymium:YAG (Nd:YAG) laser posterior capsulotomy from March 1995 to December 1997. All operations were performed by 1 surgeon using the same technique except for incision method. RESULTS: Mean interval from cataract surgery to Nd:YAG capsulotomy was 31 months in the PMMA group and 15 months in the silicone group. The difference between groups was statistically significant (P = .0002). The ratio of Elschnig pearl to fibrosis type PCO was 16:6 in the PMMA group and 14:18 in the silicone group. Mean total Nd:YAG laser energy used was 256 mJ in the PMMA group and 309 mJ in silicone group. However, the damage caused by the laser was more severe and more common in the silicone group. CONCLUSION: Silicone IOLs induced PCO faster than PMMA IOLs, with fibrosis the most common type in the silicone group. Precautions should be taken to prevent damage during Nd:YAG laser capsulotomy in eyes with a silicone IOL.

Cataract↗
PubMed1999

Two cases of late postoperative capsular block syndrome.

Two cases of late postoperative capsular block syndrome that occurred 4 and 8.5 years, respectively, were encountered. One case underwent phacoemulsification after continuous curvilinear capsulorhexis in his left eye. The other case had a can opener type capsulorhexis and underwent extracapsular cataract extraction with trabeculectomy. One-piece posterior chamber lenses were implanted in both cases. Upon slit-lamp examination, the posterior capsules were found distorted posteriorly; the capsular openings were apparently sealed by the lens optic. A whitish material existed between the intraocular lens optic and posterior capsule, with thick aggregation in a lower fifth space in case 1. After Nd:YAG laser anterior capsulotomy in case 1, the thick aggregate spread diffusely on the posterior capsule which was sunken completely for 4 weeks. After Nd:YAG capsulotomy, the distorted posterior capsule disappeared and the best corrected visual acuity was restored to 20/20 in both cases.

Capsulorhexis↗
PubMed1999

Necrosis and apoptosis after retinal ischemia: involvement of NMDA-mediated excitotoxicity and p53.

PURPOSE: Accumulated evidence has shown that apoptosis and necrosis contribute to neuronal death after ischemia. The present study was performed to study the temporal and spatial patterns of neuronal necrosis and apoptosis after ischemia in retina and to outline mechanisms underlying necrosis and apoptosis. METHODS: Retinal ischemia was induced by increasing intraocular pressure to a range of 160 mm Hg to 180 mm Hg for 90 minutes in adult rats. The patterns of neuronal cell death were determined using light and electron microscopy and were visualized by TdT-dUTP nick-end labeling (TUNEL). The mRNA expression profile of p53 was examined using reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization histochemistry. Immunohistochemistry was performed using anti-p53, anti-microtubule associated protein-2, and anti-glial fibrillary acidic protein antibodies. RESULTS: Within 4 hours after ischemia, neurons in the inner nuclear cell layer (INL) and ganglion cell layer (GCL) underwent marked necrosis, made apparent by swelling of the cell body and mitochondria, early fenestration of the plasma membrane, and irregularly scattered condensation of nuclear chromatin. After 3 days, the INL and GCL neurons showed further degeneration through apoptosis marked by cell body shrinkage, aggregation, and condensation of nuclear chromatin. Apoptotic neurons were also observed sparsely in the outer nuclear cell layer. Intravitreal injections of MK-801 prevented early neuronal degeneration after ischemia. Of note, mRNA and protein levels of p53, the tumor suppressor gene known to induce apoptosis, were increased in the retinal areas undergoing apoptosis 1 to 3 days after ischemic injury. CONCLUSIONS: Ischemia produces the N-methyl-D-aspartate-mediated necrosis and slowly evolving apoptosis of neurons in the retina. The latter may depend on the expression of the p53 proapoptosis gene.

Animals↗
PubMed1999

Reactive oxygen species-induced apoptosis and necrosis in bovine corneal endothelial cells.

PURPOSE: The loss of corneal endothelial cells associated with aging and possibly other causes has been speculated to be related to exposure to reactive oxygen species (ROS). The current study was conducted to investigate, by use of photosensitizers, the underlying mechanisms involved in the death of bovine corneal endothelial cells (BCENs) caused by ROS. METHODS: BCEN cells in primary culture were treated with a photosensitizer (riboflavin or rose bengal) with light exposure. The patterns of cell damage and death were assessed using an acridine orange-ethidium bromide differential staining method, TdT-mediated dUTP nick-end labeling (TUNEL) assay, and transmission electron microscopy. The cytotoxicity was assayed by mitochondrial function using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) testing. Antioxidants, including catalase, L-histidine, salicylic acid, and superoxide dismutase, were used to determine the types of ROS involved. Activation of nuclear factor (NF)-kappaB was examined by fluorescent immunocytochemistry with anti-p65 antibody. RESULTS: Light-irradiated riboflavin or rose bengal resulted in a significant decrease in viability of BCEN cells. Chromosomal condensation and fragmentation were observed in apoptotic cells, and membrane lysis and damage of cell ultrastructures were observed in necrotic cells. Riboflavin induced apoptosis at 30 minutes and thereafter and induced necrosis after 2 hours. Rose bengal was shown to cause similar effects within half the time required for the effects of riboflavin. Catalase and salicylic acid were found to provide protection for BCENs from cytotoxic effects of riboflavin, and L-histidine was found to protect BCENs from cytotoxicity induced by rose bengal. Kinetic studies using immunocytochemistry showed that NF-kappaB was translocated into the nucleus within 15 minutes and 30 minutes after treatment with rose bengal and riboflavin, respectively. CONCLUSIONS: The cytotoxic effects of photo-irradiated riboflavin and rose bengal are shown to be mediated by two distinct but parallel pathways, one leading to apoptosis and the other to necrosis. Possible involvement of NF-kappaB in cell death is suggested. These findings provide potential leads for future investigation into the molecular mechanisms of loss of corneal endothelial cells related to aging, oxidative stress, and possibly other similar causes.

Acridine Orange↗
PubMed1999

Role of transforming growth factor-beta in transdifferentiation and fibrosis of lens epithelial cells.

PURPOSE: To determine the levels of mRNAs encoding markers of fibrosis in lens epithelial cells (LECs) from patients with anterior polar cataracts and to test whether transforming growth factor (TGF)-beta enhances the expression of mRNAs for mesenchymal markers in LECs. METHODS: LECs attached to the anterior capsules of patients with nuclear or anterior polar cataracts were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) for the expression of mRNAs encoding pathologic extracellular matrix proteins, a marker of myofibroblast transformation, growth factors, and growth factor receptors, and by western blot analysis for the proteins encoded by these mRNAs. Bovine lens epithelial explants and intact rabbit lenses cultured with or without TGF-beta1 were also subjected to RT-PCR and western blot analysis. RESULTS: The levels of fibronectin, type I collagen, and alpha-smooth muscle actin (SMA) mRNAs were higher in LECs from patients with anterior polar cataracts than in those from patients with nuclear cataracts. Expression of mRNAs for TGF-beta1, TGF-beta2, TGF-beta receptor type II, and connective tissue growth factor (CTGF) was significantly greater in anterior polar type than in nuclear type cataracts. In contrast, expression of mRNAs for epidermal growth factor (EGF), epidermal growth factor receptor (EGFR), fibroblast growth factor (FGF)-2, and FGF receptor-1 was similar in LECs from the two types of cataracts. TGF-beta1 markedly increased the levels of fibronectin, type I collagen, and alpha-SMA mRNA in bovine lens epithelial explants and intact rabbit lenses. CONCLUSIONS: This is the first finding showing altered mRNA expression in LECs from anterior polar cataracts. Enhanced expression of TGF-beta and the TGF-beta receptor suggests that TGF-beta derived from LECs may function in an autocrine fashion as the prime mediator of transdifferentiation and pathogenesis in human LECs. Elevated levels of CTGF mRNA suggest that this growth factor may play a role in the increased deposition of extracellular matrix in metaplastic LECs.

Actins↗
PubMed1998

Reaction of Müller cells after increased intraocular pressure in the rat retina.

Using light microscopy and immunocytochemistry, we investigated the morphological changes of retinal tissues and the reaction of Müller cells in the ischemic rat retina induced by increasing intraocular pressure. At early stages (from 1 h to 24 h after reperfusion), cells in the ganglion cell layer and in the inner nuclear layer showed some degenerative changes, but at later stages (from 72 h to 4 weeks) marked degenerative changes occurred in the outer nuclear layer (ONL). At 4 weeks after reperfusion, the ONL was reduced to 1 or 2 cell layers. Immunoreactivity for glial fibrillary acidic protein (GFAP) appeared in the endfeet and distal processes of Müller cells as of 1 h after reperfusion. GFAP immunoreactivity in Müller cells increased up to 2 weeks and then decreased at 4 weeks after reperfusion. Our findings suggest that Müller cells are involved in the pathophysiology of retinal ischemia through the expression of GFAP. The degree of GFAP expression in Müller cells closely correlated with that of the degeneration of retinal neurons.

Animals↗
PubMed1998

Immunopathogenesis of experimental melanin-protein induced uveitis.

The etiology of uveitis, a general term for inflammatory disorders of the uveal tract, has not been clarified. The purpose of this study is to investigate the immunopathogenesis during experimental uveitis induced by bovine melanin associated antigen (BMAA). Experimental melanin-induced uveitis (EMIU) was induced in male Lewis rats by injection of BMAA and delayed type hypersensitivity (DTH) testing was performed. Fluorescence-activated cell sorting (FACS) analysis was used to examine expression of cell adhesion molecules with antibodies to ICAM-1 and LFA-1. BMMA-induced uveitis resembled human AAU, with onset and peak at approximately 14 and 21 days after immunization, respectively. Signs of uveitis disappeared by 4 weeks postimmunization. Histologic study revealed major infiltration of the iris and ciliary body by numerous inflammatory cells and minor infiltration of the choroid. DTH testing showed that ears injected with antigen were more swollen than non-injected ears. FACS analysis demonstrated that ICAM-1 and LFA-1 expression increased during EMIU, with ICAM-1 expression higher than that of LFA-1. In conclusion, BMAA is uveitogenically active in Lewis rats. Immunopathogenesis appeared to be mediated by cell expressing ICAM-1 and LFA-1.

Animals↗
PubMed1998

NF-kappa B activation following optic nerve transection.

In order to elucidate in vivo neuronal cell death in the retina, and involvement of NF-kappa B in this process, we studied the degeneration of retinal ganglion cells (RGCs) and the activation of NF-kappa B after transection of the optic nerve of adult rat at 5 mm from the eyeball. The morphology of dying ganglion cells in the retinal ganglion cell layer was observed by light and electron microscopy, the activation of NF-kappa B was investigated immunohistochemically. Seven and 14 days post-axotomy, dying cells contained pyknotic nuclei. The death of retinal ganglion cells involved apoptosis, activation of NF-kappa B (p50 and p65) was prominent in a time dependent manner. We observed axotomy-induced NF-kappa B activation, which may mediate apoptosis of retinal ganglion cells.

Animals↗
PubMed1997

Protein purification and nucleotide sequence of a lysozyme from the bacteria-induced larvae of the fall webworm, Hyphantria cunea.

A protein with lytic activity against Micrococcus luteus was purified from the hemolymph of the fall webworm, Hyphantria cunea, larvae challenged with live E. coli. A bacteriolytic protein of about 14,000 daltons in mass was purified by cation exchange chromatography and reverse-phased HPLC. The optimum pH and optimum temperature range for activity were around pH 6.2 and 50 degrees C, respectively, in a 100 mM phosphate buffer. The amino-terminal amino acid sequence of this protein was determined and the corresponding cDNA was isolated and analyzed. The deduced protein of 142 amino acid residues was composed of a putative leader sequence of 20 residues and the mature enzyme of 122 residues. The cloned lysozyme gene was strongly induced in response to bacterial injection, implying that the enzyme is a part of the immune response of H. cunea. Comparison with other known lysozyme sequences shows that our lysozyme belongs to the chicken lysozyme.

Amino Acid Sequence↗
PubMed1997

Computer-assisted videokeratography to measure changes in astigmatism induced by sutureless cataract surgery.

PURPOSE: To compare the visual outcome, change in surgically induced astigmatism, and corneal thickness after sutureless cataract surgery through either a scleral tunnel or clear corneal incision. SETTING: Department of Ophthalmology, Kangnam St. Mary's Hospital, Catholic University Medical College, Seoul, Korea. METHODS: This retrospective study evaluated 79 eyes of 64 patients who had cataract surgery using a 6.0 mm scleral tunnel incision (Group 1, n = 20 eyes), 3.1 mm clear corneal incision at the 10 o'clock position (Group 2, n = 35 eyes), or 3.1 mm clear corneal incision at the 10 o'clock position (Group 3, n = 24 eyes). Changes in surgically induced astigmatism were analyzed using computer-assisted videokeratography (CVK) 1 day, 8 weeks, and 6 months postoperatively. RESULTS: Eleven eyes (55.0%) in Group 1, 15 (42.8%) in Group 2, and 11 (48.5%) in Group 3 had an uncorrected visual acuity of 20/40 or better 1 day postoperatively. The CVK measurements showed significantly more flattening at radial distances of 0.75, 1.50, and 2.50 mm along the 90 degree semimeridian in Group 2 than in Group 1 (P < .05) 1 day after surgery; in Group 3, flattening along the incisional semimeridian fell between the amounts in Groups 1 and 2. At 8 weeks, the amount of flattening decreased in all groups, and the differences between groups were not statistically significantly different (P > .05). In the CVK pattern, corneal flattening along the incisional meridian was narrower and longer in Groups 2 and 3 than in Group 1. CONCLUSION: Localized flattening along the incisional meridian was prominent temporally after clear corneal incision surgery. However, there was no difference in early visual rehabilitation between the clear corneal and scleral tunnel incision groups.

Adult↗
PubMed1997

Phacoemulsification with a bevel-down phaco tip: phaco-drill.

We present a technique for in situ lens nucleus emulsification using low phaco power and high vacuum, a continuous curvilinear capsulorhexis, and hydrodelineation. Emulsification is done with the phaco tip slanted down 30 or 45 degrees. Cutting and aspiration do not cause an undesirable energy loss. This technique can be combined with the nuclear chopping or divide and conquer methods because of its ability to drill and hold the nucleus. Posterior capsular rupture is prevented because the separated epinucleus acts as a barrier between the nucleus and the cortex. The low power used minimizes the energy transfer to the corneal endothelium. This technique is particularly useful in eyes with brunescent cataract.

Humans↗
PubMed1996

Capsular opening contraction after continuous curvilinear capsulorhexis and intraocular lens implantation.

PURPOSE: To evaluate the progressive constriction of the anterior capsule opening that can occur after continuous curvilinear capsulorhexis (CCC). SETTING: Kangnam St. Mary's Hospital, Seoul, Korea. METHODS: Changes in the anterior capsule opening after CCC were evaluated in 166 pseudophakic eyes at 1 week and 1 and 3 months postoperatively. The capsular opening diameter was measured with an image analysis system. RESULTS: The capsular opening diameter was reduced by an average of 13.87% 3 months after CCC. There was more dense opacity in the anterior than in the posterior capsule. Lens epithelial cells (LECs) were the main cause of capsule contraction; sex, age, intraocular lens haptic length and haptic material, and CCC size did not have a statistically significant effect on capsule shrinkage (P > .05). Three months after surgery, most eyes with an initial capsular opening diameter of less than 5.5 mm had an opening diameter smaller than 5.0 mm. In most eyes with an initial capsular opening larger than 5.5 mm, the opening remained larger than 5.0 mm. CONCLUSION: Our results suggest that the ideal CCC size is 5.5 to 6.0 mm or larger and that LEC removal is necessary to preserve the pupillary zone and thus prevent progressive capsular opening shrinkage.

Adult↗