Ryoji Yamakawa

Cell Components in Proliferative Vitreoretinopathy: Immunofluorescent Double Staining of Cultured Cells from Proliferative Tissues

Intermediate filament proteins in cultured cells from epiretinal membranes of 5 cases of proliferative vitreoretinopathy and subretinal strands of 2 cases were immunohistologically characterized. Double staining technique after colcemid treatment revealed that either keratin-positive or vimentin-positive cells were found with different ratios depending on the cases. Both positive and both negative cells were also observed. Desmin and glial fibrillary acidic protein were totally negative.

DNA Aptamer Raised against Advanced Glycation End Products Prevents Abnormalities in Electroretinograms of Experimental Diabetic Retinopathy

Purpose: Abnormalities in electroretinograms (ERG), such as reduced amplitudes and delayed implicit times of a- and b-wave and oscillatory potentials (OPs), are one of the earliest features of diabetic retinopathy prior to obvious vascular changes in diabetic retinas. We have previously shown that serum levels of advanced glycation end products (AGEs) are correlated with a delayed latency of OPs in type 2 diabetic rats. However, the pathological role of AGEs in ERG abnormalities remains unclear. We examined here whether high-affinity DNA aptamer directed against AGEs (AGE-aptamer) prevents ERG abnormalities in experimental type 1 diabetic retinopathy. Methods: Streptozotocin-induced diabetic rats or control rats received continuous intraperitoneal infusion of either AGE-aptamer or control aptamer via an osmotic mini pump for 16 weeks. Anthropometric, metabolic, and hemodynamic variables were measured, and an ERG was performed. Results: Although AGE-aptamer did not affect body weight, fasting and random blood glucose, HbA1c, blood pressure, or lipid parameters, it completely prevented the increase in serum AGE levels as well as the reduction of a- and b-wave and OP amplitudes in diabetic rats. Conclusion: The present study demonstrated for the first time that AGE-aptamer prevents abnormalities in ERG in experimental diabetic retinopathy probably by blocking the harmful effects of AGEs.

Effects of Phenothiazines on Cultured Retinal Pigment Epithelial Cells

Phenothiazines (chlorpromazine, trifluoperazine, prochlorperazine, and fluphenazine) showed dose-dependent inhibition of phagocytosis of latex particles by cultured chick retinal pigment epithelial cells at concentrations of 10(-5)-10(-14) mol/l. Calmodulin antagonists (W-5, W-7, W-12, and W-13) showed similar effects as phenothiazines at concentrations of 10(-5)-10(-14) mol/l. These reactions were partially reversible at a concentration of 10(-9) mol/l. Cells cultured for 3 days in the presence of 10(-5) mol/l chlorpromazine or 10(-5) mol/l W-7 demonstrated morphologic alterations in their microvilli which were similar to those seen after cytochalasin B treatment, i.e., thinning and elongation of the microvilli with honeycomb-like changes.

Involvement of fibronectin in in vitro regeneration of retinal pigment epithelium

Argon laser photocoagulation was placed on the confluent monolayer of cultured chick retinal pigment epithelial cells as a model of the regeneration process of retinal pigment epithelium after laser burn. The intense fibrillar net immunofluorescent pattern of fibronectin appeared on the burnt area from 2 h after the laser application, before the beginning of tissue reconstruction. Fibronectin was observed for several days, then became undetectable before the complete regeneration of retinal pigment epithelial cells. This indicates that fibronectin is involved in the early regeneration process of retinal pigment epithelium.

Retinal pigment epithelial cells produce fibronectin.

Antichick fibronectin antiserum, noncross-reactive to bovine fibronectin, was prepared to determine the production of fibronectin by cultured chick retinal pigment epithelial cells which were grown in the presence of fetal bovine serum. The typical fibrillary net pattern of fibronectin was observed by an indirect immunofluorescent technique when this specific antiserum reacted with cultured chick retinal pigment epithelial cells. Cultured chick retinal pigment epithelial cells were shown to produce fibronectin.

Subretinal strands. Tissue culture and histological study

Subretinal strands in proliferative vitreoretinopathy removed during vitreous surgery in ten cases were studied histologically; tissue culture was taken from five of the ten cases to obtain more material for investigation. Tissue culture was successful in all five cases. The cultured tissue just next to the original strand preserved the characteristics of the original tissue, whereas the portion distal from the original strand did not. Definite and/or suspected retinal pigment epithelial cells (RPE) were found in seven of ten original strands and four of five samples of cultured material. RPE were considered to be a predominant component of subretinal strands.

Exocytosis by Retinal Pigment Epithelial Cells

We observed cultured retinal pigment epithelial cells as they responded to the introduction of latex particles. The cells showed phagocytosis of particles 1 h after administration of latex and were filled with particles after 24 h. After 7 days, exocytosis of latex from basal plasma membrane was documented. Observation was repeated using a two-layer culture. 7 days after putting the retinal pigment epithelial layer containing latex particles on another layer without particles, we observed the appearance of latex particles in the lower layer that originally contained no particles. This demonstrated that cultured retinal pigment epithelial cells exocytose latex particles from basal cell membrane.

Macular ganglion cell complex measurement in bilateral retrobulbar optic neuropathy without a relative afferent pupillary defect

Purpose This study aimed to demonstrate the clinical usefulness of measuring the macular ganglion cell complex (GCC) for the early detection of axonal loss in eyes with bilateral retrobulbar optic neuropathies. Patients and methods We retrospectively reviewed the medical records of three patients with bilateral toxic, ischemic, or infiltrative retrobulbar optic neuropathy. Results No relative afferent pupillary defect was detected in any patients. The results of the fundus examinations were unremarkable at the initial presentation except for slight optic disk pallor in the right eye of Case 3. Magnetic resonance imaging showed no abnormal findings in Cases 1 and 2. Measurement of the macular GCC clarified the presence of axonal loss in all three cases with diagnostic uncertainty. Although reduction in the macular GCC thickness was not observed initially in Case 2, it became evident later when both optic disks still appeared normal. Conclusion A reduction in the macular GCC thickness seemed to precede the appearance of optic disk pallor and occurs regardless of toxic, ischemic, or infiltrative retrobulbar optic neuropathy. The current case series suggested that measurement of the macular GCC facilitated early differentiation between bilateral retrobulbar optic neuropathy and nonorganic visual loss, which can otherwise be challenging in some cases.

Recurrent pterygium treatment using mitomycin C, double amniotic membrane transplantation, and a large conjunctival flap

Purpose The aim of this study was to evaluate the clinical outcomes of surgery for recurrent pterygia using mitomycin C (MMC), double amniotic membrane transplantation (AMT), and a large conjunctival flap. Patients and methods This retrospective case series included 31 eyes in 31 patients with recurrent pterygia. All patients underwent pterygium excision, application of MMC, double AMT, and placement of a large conjunctival flap. Outcome measures were visual acuity, astigmatism, and recurrence. Recurrence was defined as the presence of fibrovascular proliferative tissue crossing the limbus. Results The patients’ mean age was 68.2 years. The mean follow-up period was 3.6 years. The mean preoperative and postoperative best-corrected visual acuities (logMAR conversion) were 0.23 and 0.13, respectively. There was a significant difference between the mean preoperative (−3.85 D) and postoperative (−2.22 D) astigmatism. The recurrence rate was 3.2% (1/31 cases). Conclusion Surgical pterygium excision with application of MMC, double AMT, and placement of a large conjunctival flap was an effective treatment for recurrent pterygia.

VITRECTOMY FOR MACULAR RETINOSCHISIS WITHOUT A DETECTABLE OPTIC DISK PIT.

Purpose: To evaluate the efficacy of vitrectomy in the treatment of macular retinoschisis without a detectable optic disk pit. Methods: This retrospective interventional case series included eight patients with acquired, unilateral macular retinoschisis with or without foveal detachment. Patients with an optic disk pit, vitreomacular traction, or high myopia were excluded. Six of the eight patients underwent vitrectomy with internal limiting membrane peeling and fluid-air exchange. The surgical outcome was evaluated in terms of the improvement in the macular anatomy and the best-corrected visual acuity. Results: During vitrectomy, all the six eyes were confirmed to have preexisting posterior vitreous detachment. Macular retinoschisis was resolved or reduced in all the six eyes after vitrectomy. The mean central foveal thickness showed significant improvement at the time of the patients final visit after vitrectomy. The mean best-corrected visual acuity was 20/52 before surgery and 20/31 at the final visit. Conclusion: Vitrectomy might be effective for the treatment of macular retinoschisis without an optic disk pit. Although clinically similar to optic pit maculopathy except for the absence of pit, our intraoperative observations of the posterior hyaloid membrane suggest that maculopathy without optic disk pit has a distinct pathogenesis.