Tomomi Higashide

Roles of the AGE-RAGE system in vascular injury in diabetes

Abstract: This study concerns whether advanced glycation endproducts (AGE) are related to microvascular derangement in diabetes, exemplified by pericyte loss and angiogenesis in retinopathy and by mesangial expansion in nephropathy. AGE caused a decrease in viable pericytes cultivated from bovine retina. On the other hand, AGE stimulated the growth and tube formation of human microvascular endothelial cells (EC), this being mediated by autocrine vascular endothelial growth factor. In AGE‐exposed rat mesangial cells, type IV collagen synthesis was induced. Those AGE actions were dependent on a cell surface receptor for AGE (RAGE), because they were abolished by RAGE antisense or ribozyme. The AGE‐RAGE system may thus participate in the development of diabetic microangiopathy. This proposition was supported by experiments with animal models; several indices characteristic of retinopathy were correlated with circulating AGE levels in OLETF rats. The predisposition to nephropathy was augmented in RAGE transgenic mice when they became diabetic.

Upregulation of Retinal Vascular Endothelial Growth Factor mRNAs in Spontaneously Diabetic Rats without Ophthalmoscopic Retinopathy

Vascular endothelial growth factor (VEGF) has recently been shown to be involved in the pathogenesis of proliferative diabetic retinopathy. However, its involvement in the development of the early phase of diabetic retinopathy is not fully understood. In this study we investigated the retinal VEGF mRNA level in spontaneously diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats, a model of non-insulin-dependent diabetes, without overt retinopathy, using quantitative reverse-transcription polymerase chain reaction. The retinal VEGF mRNA level was 2.2 times higher (p < 0.0005) in OLETF rats than in control rats at the age of 60 weeks. Moreover, their retinal mRNA level was positively correlated with serum concentration of advanced glycation end products (AGEs) but not to serum glucose concentration. Furthermore, the peak latency of the oscillatory potentials in the electroretinogram, one of the most sensitive markers for the early phase of diabetic retinopathy, was significantly prolonged in OLETF rats (p < 0.05), being also correlated with the serum AGE concentration. The results thus suggest that AGEs, which are formed acceleratedly in diabetic conditions, are involved in the development of the early phase of diabetic retinopathy probably through the induction of retinal VEGF mRNAs.

Cloning of the cDNA for a Novel Photoreceptor Protein

A subtractive cDNA cloning strategy was used to isolate a 1381-base pair human retina-specific cDNA, human retinal gene 4 (HRG4), which hybridized to a 1.4-kilobase message in the retina and encoded a 240-amino acid acidic protein with a calculated molecular mass of 26,964 Da. The proximal of the conceptual protein sequence was rich in glycine (18%) and proline (20%), had a predicted secondary structure of turns, and showed a loose similarity (19-24%) to various α-collagen sequences, while the distal consisted of a mixture of α-helices, β-sheets, and turns. Genomic Southern analysis with HRG4 showed cross-hybridizing sequences in six different species, and HRG4 was 92% homologous with a 1264-base pair rat cDNA (rat retinal gene 4; RRG4) at the protein level. The region of 100% identity between the two sequences corresponded to the distal of the protein sequence consisting of mixed secondary structures, suggesting a functionally important domain. In vitro transcription and translation corroborated the open reading frames corresponding to HRG4 and RRG4 in the cDNAs. Expression of HRG4 in the retina was localized to the photoreceptors by in situ hybridization. Developmentally, RRG4 began to be highly expressed around postnatal day 5 in the rat outer retina when the photoreceptors begin to differentiate and rapidly increased in expression to reach the mature adult level by postnatal day 23. No diurnal fluctuation in expression of RRG4 was seen.

Unilateral choroidal excavation in the macula detected by spectral‐domain optical coherence tomography

Purpose:  To report clinical findings of three patients with unilateral peculiar choroidal excavation in the macula detected by spectral‐domain (SD) optical coherence tomography (OCT).

Beneficial effects of preoperative intravitreal bevacizumab on trabeculectomy outcomes in neovascular glaucoma

Purpose:  This study aimed to investigate the effects of preoperative intravitreal bevacizumab (IVB) on outcomes in trabeculectomy for neovascular glaucoma (NVG).

In Vivo Quantitative Evaluation of the Rat Retinal Nerve Fiber Layer with Optical Coherence Tomography

PURPOSE To determine whether optical coherence tomography (OCT) is useful for quantitative evaluation of the thickness of the rat retinal nerve fiber layer (RNFL) in an optic nerve crush model. METHODS An OCT system was developed with a modified commercial time-domain OCT and a superluminescent diode with a bandwidth of 150 nm. Optical components were optimized to acquire rat retinal images. The right optic nerve was crushed intraorbitally with a clip. The left eye served as the untreated control. Circumpapillary OCT scans with a circle diameter of 500 microm centered on the optic disc were performed before and 1, 2, and 4 weeks after the crush. Repeatability and reproducibility of RNFL thickness measurements were evaluated. The RNFL thicknesses at 400, 500, and 600 microm from the center of the optic disc determined by linear vertical OCT scans were compared with thicknesses in retinal sections. RESULTS The mean RNFL thicknesses in circumpapillary OCT scans were 27.9 +/- 1.8, 29.2 +/- 2.4, 19.9 +/- 2.3, and 4.5 +/- 3.6 microm before and 1, 2, and 4 weeks after the crush, respectively. RNFL thickness was unchanged 1 week after the crush, but then decreased significantly and progressively after the second week (P < 0.01). Coefficients of repeatability and reproducibility were less than 10% except for the crushed eyes at 4 weeks. RNFL thicknesses in OCT images correlated significantly with thicknesses determined histologically (r = 0.90, P < 0.001). CONCLUSIONS OCT is a useful and valuable tool for quantitative evaluation of rat RNFL thickness.

Immunolocalization of X-arrestin in human cone photoreceptors

X‐arrestin is a recently identified retina‐specific gene of unknown function. Affinity‐purified anti‐peptide antibody to human X‐arrestin was prepared, and used in Western blot analysis of human retinal proteins and for immunohistochemistry on human retinal sections. By Western blot analysis, the antibody specifically bound to an ≈47 kDa protein, and by indirect immunofluorescence specifically labeled cone photoreceptors with greatest intensity in their outer segments. In single and double label experiments, the localization of X‐arrestin immunoreactivity was compared with immunolabelling patterns obtained with antibodies to red/green cone opsin, rhodopsin, and S‐antigen. The results showed that X‐arrestin is expressed in red‐, green‐ and blue‐sensitive cones in the human retina.

Does the enlargement of retinal nerve fiber layer defects relate to disc hemorrhage or progressive visual field loss in normal-tension glaucoma?

PurposeWe investigated the difference in clinical characteristics between cases with enlarged retinal nerve fiber layer defects (RNFLD) and stable RNFLDs in normal-tension glaucoma (NTG). Patients and MethodsWe retrospectively reviewed NTG patients that were diagnosed and followed up for at least 3 years at 1-month to 2-month intervals by the same examiner, and selected eyes with distinct RNFLD borders. Using fundus photographs, for which we extracted only a blue ingredient and processed it into black and white, we measured RNFLD angles and divided NTG cases into 2 groups, enlarged RNFLD and stable RNFLD, and compared the clinical characteristics between both groups. ResultsNinety-three eyes from 93 patients (mean follow-up, 8.2 y) were selected and enlargement of RNFLD was detected in 55 eyes. Disc hemorrhage (DH) was found in 35 of 55 eyes (63.6%) in the enlarged group and in 6 of 38 eyes (15.8%) in the stable group (P<0.0001). Twenty-one eyes (38.2%) from the enlarged group exhibited recurrent DH. In 48 eyes (87.3%) from the enlarged group, the enlargement of RNFLD was toward the fovea. When DHs located apart from RNFLD were excluded, RNFLD enlarged in the direction of DH in 21 of 25 eyes (84.0%). The cumulative probability of non progression in the visual field was significantly lower in the enlarged group (10–year survival rate: 0.52±0.11) than in the stable group (10-year survival rate: 0.89±0.08) (P=0.0019). ConclusionsThe enlargement of RNFLD in NTG was closely associated with DH occurrence and the deterioration of visual field.

Focal relationship between structure and function within the central 10 degrees in glaucoma.

PURPOSE To investigate which measurements of inner macular thickness are the most useful for evaluating the focal relationship with visual sensitivity within the central 10° in glaucoma and which layers require correction for retinal ganglion cell (RGC) displacement. METHODS Sixty eyes of 60 subjects with glaucoma were included. Sensitivity of each test point of 10-2 standard automated perimetry was compared with the thickness of the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), GCL+ inner plexiform layer (IPL), and RNFL+GCL+IPL (GCC), with and without RGC displacement, using Spearmans rank correlation coefficients. Visual sensitivity was evaluated by unlogged 1/Lambert (1/L) values. RESULTS Retinal nerve fiber layer thickness correlated significantly with the sensitivities of all test points except for some in the papillomacular bundle region when adjusting for RGC displacement (rs = 0.287-0.767, P < 0.05). In the central 5.8°, the GCL and (GCL+IPL) thickness correlated significantly with the sensitivities of all test points when adjusting for RGC displacement (GCL: rs = 0.363-0.729, P < 0.01; (GCL+IPL): rs = 0.359-0.715, P < 0.01). The GCC thickness correlated significantly with the sensitivities of all 68 test points when adjusting for RGC displacement (rs = 0.359-0.767, P < 0.01). RGC displacement improved the correlation between sensitivity and GCL, (GCL+IPL), and GCC in the central 4 points (GCL: rs = from 0.270-0.470 to 0.421-0.540; (GCL+IPL): rs = from 0.195-0.450 to 0.381-0.549; GCC: rs = from 0.132-0.449 to 0.359-0.562). CONCLUSIONS The GCC is the most useful parameter to evaluate structure and function within the central 10° in glaucoma. Adjusting for RGC displacement is essential to evaluate the relationship between structure of the GCL-related layer and function at the central macula.

Endophthalmitis Caused by Enterococcus mundtii

ABSTRACT Enterococcus mundtii has rarely been isolated from environmental or human sources. We report the identification of E. mundtii as a pathogen of human infectious disease by DNA sequencing of 16S rRNA and sodA genes in a case of endophthalmitis developed in a 66-year-old immunocompetent gardener.