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Taiichi Hikichi

Publications and source records attributed to Taiichi Hikichi.

13 recordsLinked to original sources
PubMed2005

Adenosine agonist regulation of outward active transport of fluorescein across retinal pigment epithelium in rabbits.

To investigate the effect of an adenosine agonist, 2-5'-N-ethylcarboxamidoadenosine (NECA), on the outward active transport of fluorescein across the retinal pigment epithelium (RPE) in rabbits. High (5x10(-4)-2x10(-3) M) and low (1x10(-5)-1x10(-4) M) concentrations of NECA or phosphate buffered saline (PBS) were intravitreously injected into Dutch-belted rabbits. Sodium fluorescein was injected intravenously 180 min after NECA. Differential vitreous fluorophotometry was performed 3 hr after the sodium fluorescein injection and the vitreal fluorescein/fluorescein monoglucuronide (F/FG) ratio then was calculated. The F/FG ratios are inversely proportional to the outward active transport of fluorescein across the RPE. Retinal detachments were induced by injection of PBS into the subretinal space after the intravitreous injection of low- or high-dose NECA or PBS, and the size of the blebs was monitored. In eyes that received a low-dose injection of NECA, the F/FG ratio was higher compared with controls (P<0.05); in eyes that received a high-dose intravitreal injection, the F/FG ratio was significantly lower compared with controls (P<0.05). The effect of low-dose NECA on the F/FG ratio was suppressed by the A2 receptor antagonist, ZM241385, and the effect of high-dose NECA was suppressed by the A1 receptor antagonist, 8-cyclopentyl-1, 3-dipropylxanthine. The A3 receptor antagonist MRS1191 did not influence the effect of low- or high-dose NECA. Intravitreal injection of high-dose NECA enhanced the reabsorption of subretinal fluid compared with PBS; however, low-dose NECA inhibited reabsorption of subretinal fluid (P<0.02 and 0.05, respectively). Intravitreous injection of high-dose NECA accelerates the active outward transport across the RPE via A1 receptors and low-dose NECA decelerates it via A2 receptors.

Adenosine↗
PubMed2004

Irregularity of photoreceptor layer after successful macular hole surgery prevents visual acuity improvement.

PURPOSE: To investigate the association between a photoreceptor irregularity and visual acuity (VA) after macular hole (MH) surgery. DESIGN: Prospective observational case series. METHODS: Twenty-four eyes with an idiopathic MH that resolved after vitreous surgery were examined by new optical coherence tomography (OCT 3000). The images were divided into regular photoreceptor, detected as a straight line above the retinal pigment epithelium reflex, and irregular, which cannot be detected by it. RESULTS: Regular images were observed in 12 eyes (80%) and irregular images in 3 eyes (20%) with good VA (>or=0.7). Regular images were seen in 3 eyes (33%) and irregular images in 6 eyes (67%) with poor VA (<0.7). The percentage of regular images in the group with good VA was significantly higher than that in the group with poor VA (P <.05). CONCLUSION: A photoreceptor irregularity after MH surgery may prevent VA improvement.

Aged↗
PubMed2004

Effect of nucleotide P2Y2 receptor agonists on outward active transport of fluorescein across normal blood-retina barrier in rabbit.

BACKGROUND: To evaluate the effect of nucleotide P2Y(2) receptor agonists INS542 and uridine 5'-triphosphate (UTP) on the outward active transport of fluorescein across rabbit blood-retina barrier (BRB) in vivo. METHODS: Injection (0.1 ml) of INS542 (0.1 or 1mM), phosphate buffered solution, or UTP (1 or 10mM) was made in Dutch-belted rabbits. Differential vitreous fluorophotometry (DVF) was performed 3hr later and the fluorescein (F)/fluorescein monoglucuronide (FG) ratio was then calculated. F/FG ratios are inversely proportional to outward active transport of F across BRB at the level of the retinal pigment epithelium (RPE). In another set of experiments, the effect of 0.1 ml vitreous injection of INS542 (1mM) on F/FG ratios was evaluated at different time points ranging from 0.5 to 48hr before conducting DVF. RESULTS: F/FG ratios obtained 3hr after intravitreal injection were as follows (mean+/-standard error): 0.49+/-0.14 (0.1mM INS542), 0.19+/-0.04 (1mM INS542), 0.48+/-0.09 (PBS), 0.40+/-0.08 (1mM UTP) and 0.36+/-0.05 (10mM UTP). The F/FG ratio for 1mM INS542 was significantly lower than in the other groups (P<0.05). In the time course experiments, a significant decrease in the F/FG ratios was observed between 1 and 12hr following administration of INS542 when compared with F/FG ratios obtained in the contralateral (untreated) eye. CONCLUSION: Intravitreal administration of INS542 (but not UTP) enhances outward active transport of F across RPE in intact rabbit eye, indicating that activation of P2Y(2) receptors in vivo directly stimulates RPE active transport.

Animals↗
PubMed2004

Time course of development of posterior vitreous detachment in the fellow eye after development in the first eye.

PURPOSE: To determine when posterior vitreous detachment (PVD) develops in the fellow eye after development in the first eye. DESIGN: Prospective, observational case series. PARTICIPANTS: Fifty-one patients with acute unilateral PVD participated in the study. METHODS: All patients underwent a comprehensive ocular examination, including a dynamic vitreous examination using biomicroscopy with and without a preset lens and retinal examination with scleral depression, every 3 months at least until PVD developed in the fellow eye. RESULTS: Posterior vitreous detachment developed in 4 eyes (8%) within 6 months, 12 eyes (24%) within 1 year, 24 eyes (47%) within 18 months, 33 eyes (65%) within 2 years, 41 eyes (80%) within 30 months, and 46 eyes (90%) within 3 years. In 5 eyes (10%), PVD did not develop during the follow-up period of more than 3 years. CONCLUSIONS: Posterior vitreous detachment develops frequently in the fellow eye from 6 months to 2 years after development in the first. These findings are useful for the management of patients with unilateral PVD.

Aged↗
PubMed2002

Association of preoperative photoreceptor displacement and improved central scotoma after idiopathic macular hole surgery.

OBJECTIVE: To investigate the relationship between preoperative photoreceptor displacement and postoperative scotoma after unilateral idiopathic macular hole surgery. DESIGN: Prospective nonrandomized comparative self-controlled trial. PARTICIPANTS: Twenty patients who underwent successful surgery for unilateral idiopathic macular hole participated in the study. METHODS: Kinetic perimetry using red and green filter glasses, black binocular fixation targets, and red and green selective monocular stimuli was performed preoperatively. Scanning laser ophthalmoscope (SLO) microperimetry was performed preoperatively and postoperatively. RESULTS: Sixteen patients had photoreceptor displacement preoperatively. In preoperative SLO microperimetry, all eyes with a macular hole had a scotoma; postoperatively, 12 of 16 had no scotoma. All four eyes with no preoperative photoreceptor displacement were noted to have a postoperative scotoma. The prevalence of postoperative scotoma in patients with preoperative photoreceptor displacement (4 of 16; 25%) was significantly lower than that in patients without preoperative photoreceptor displacement (4 of 4; 100%) (P = 0.03). CONCLUSIONS: The presence or absence of photoreceptor displacement preoperatively should affect postsurgical visual function. Photoreceptor damage may occur in eyes without photoreceptor displacement preoperatively, resulting in scotoma postoperatively.

Aged↗
PubMed2002

Inhibitory effect of bucillamine on laser-induced choroidal neovascularization in rats.

PURPOSE: We investigated the inhibitory effects of bucillamine on formation of laser-induced choroidal neovascularization (CNV) in a rat model. METHODS: Bucillamine administration (approximately 150 mg/kg/day) was started 1 week before photocoagulation and continued to the end of the study. Control groups received drinking water. Two weeks after photocoagulation, choroidal neovascularization development was evaluated using simultaneous fluorescein and indocyanine green angiography, and the maximal thickness of the lesions was measured histologically. RESULTS: The incidence of CNV formation was 99.5 +/- 0.2% [mean +/- standard deviation (SD)] in control rats and 64.3 +/- 15.1% with bucillamine (P < 0.01). Histological study showed that the thickness of the CNV lesions was 23.4 +/- 6.5 microm (mean +/- SD) in the bucillamine-treated rats, which was significantly decreased compared to that in controls (60.8 +/- 9.2 microm) (P < 0.01). CONCLUSIONS: Our results suggest that bucillamine may inhibit the development of laser-induced CNV in rats.

Animals↗
PubMed2002

Inhibitory effects of bucillamine on increased blood-retinal barrier permeability in streptozotocin-induced diabetic rats.

PURPOSE: To investigate the effect of bucillamine for prevention of increasing blood-retinal barrier (BRB) permeability in streptozotocin (STZ)-induced diabetic rats. METHODS: The groups included control and STZ-induced diabetic rats treated with or without bucillamine. Six months after intervention, the concentrations of reduced and oxidative glutathione (GSH and GSSG) in the retina were measured biochemically. In addition, vitreous fluorescein, which leaks from the vessels after intravenous injection of fluorescein sodium, was measured to evaluate BRB permeability. To evaluate the scavenging ability against the reactive oxygen species (ROS) in vitro, the second-order rate constant for the reaction of bucillamine with ROS was estimated from the kinetics based on the rate constant for the reaction of ROS. RESULTS: The BRB permeability was significantly higher (p = 0.01) in diabetic rats not treated with bucillamine, and bucillamine inhibited the BRB permeability. The GSH concentration and the GSH/GSSG ratio in the retinas decreased in diabetic rats not treated with bucillamine; bucillamine inhibited the decrease of the GSH concentrations. The ROS scavenging activity of bucillamine was similar with that of GSH. CONCLUSIONS: In diabetic retinas, oxidative stress might increase, which may be one of the causes of BRB breakdown. The antioxidant effects of bucillamine might take part in inhibition of increased permeability of the BRB in diabetes.

Animals↗
PubMedDate not supplied

Inhibitory effect of bucillamine on the increased leukocyte entrapment in the retinal microcirculation of diabetic rats.

PURPOSE: To evaluate quantitatively the effects of bucillamine on the entrapment of leukocytes in the retinal microcirculation of diabetic rats. METHODS: 13 male Brown Norway rats were injected with streptozotocin (STZ). After the animals developed diabetes, they were divided into two groups. Group 1 (n=7) received fresh drinking water without bucillamine, and group 2 (n=6) received fresh drinking water supplemented with bucillamine (200 mg/kg per day). Rats that were not injected with STZ and received water without bucillamine served as controls (n=6). Four weeks after the injection of STZ, the leukocytes in the retina were observed by acridine orange digital fluorography. The number of leukocytes trapped in the retinal vessels was compared among the three groups. RESULTS: In the untreated diabetic rats, the number of trapped leukocytes was significantly higher than in control rats or bucillamine-treated diabetic rats (P<0.05). CONCLUSIONS: We demonstrated an inhibitory effect of bucillamine on leukocyte entrapment in the retinal vessels of diabetic rats. Bucillamine may have therapeutic efficacy in preventing the development of diabetic retinopathy.

Animals↗
PubMedDate not supplied

Use of scanning laser ophthalmoscope microperimetry in clinically significant macular edema in type 2 diabetes mellitus.

PURPOSE: We used scanning laser ophthalmoscope (SLO) microperimetry to evaluate scotomas in patients with clinically significant diabetic macular edema (CSME) in type 2 diabetes mellitus. METHODS: We studied 19 patients (mean age = 63 years; range, 45-78 years) (19 eyes). SLO microperimetry was performed in all eyes. We divided patients into three groups as follows: dense scotoma, relative scotoma, and no scotoma. The following variables were documented: age; duration of diabetes, hemoglobin A(1c) levels; logarithm of the minimum angle of resolution (Log(MAR)) visual acuity; refractive power; a history of panretinal photocoagulation; presence or absence of proliferative diabetic retinopathy, vitreomacular separation, and cystoid changes; the type of macular edema; and stability of fixation. All variables were compared in the three groups. RESULTS: We identified 4 eyes (21.1%) with dense scotoma, 10 (52.6%) with relative scotoma, and 5 (26.3%) with no scotoma. There were significant differences in log(MAR) visual acuity among those with dense scotoma (1.4 +/- 0.5), relative scotoma (0.6 +/- 0.2), and no scotoma (0.2 +/- 0.3) (P <.05), and in the prevalence of cystoid changes, diffuse edema, and unstable fixation among those with dense scotoma (75%, 75%, and 100%, respectively), relative scotoma (20%, 30% and 50%, respectively) and no scotoma (0%, 0% and 0%, respectively) (P <.05). CONCLUSIONS: Macular scotoma was observed by SLO microperimetry in 74% of the patients in this study. A scotoma in CSME is related to the formation of cystoid changes and the type of macular edema. In eyes with CSME in type 2 diabetes mellitus, a scotoma in the macula causes visual acuity impairment and unstable fixation.

Aged↗
PubMedDate not supplied

Effects of latanoprost on blood-retinal barrier permeability in rabbits.

PURPOSE: To investigate the effect of latanoprost (LP) on the inward and outward permeability (Pin and Pout) of the blood-retinal barrier (BRB). METHODS: Four New Zealand white rabbits received topical LP (0.005%) once daily for 3 weeks in one eye and phosphate-buffered saline (PBS) in the fellow eye (topical group). Five New Zealand white rabbits were injected intravitreously with LP (0.1 ml, 0.005%) in one eye and PBS (0.1 ml) in the fellow eye (injection group). In the injection group, vitreous fluorophotometry (VFP) to estimate the Pin and differential vitreous fluorophotometry (DVF) to estimate the Pout were performed 60 min after LP was injected. After the baseline measurements, VFP and DVF were performed 60 and 180 min after intravenous injection of sodium fluorescein, respectively. Fluorescein (F) and fluorescein monoglucuronide (FG) concentrations were obtained by DVF, and the F/FG ratio was calculated as an index of the Pout. RESULTS: In the topical group, there were no significant differences in the Pin or F/FG ratio between the LP- and the PBS-treated eyes. In the injection group, the Pin in the LP-treated eyes was significantly higher than in PBS-treated eyes (p < 0.05). There was no significant difference in the F/FG ratio between the two groups. CONCLUSION: Although we cannot exclude the effect of differences in species, the physiologic effect of LP, which increased the Pin, was seen in experimental studies. Because antiglaucoma drugs are generally used over an extended period, further clinical studies of the effect of LP on the BRB should be performed in patients who have BRB breakdown, such as in uveitis, and in patients who are pseudophakic and aphakic.

Administration, Topical↗