Physical interaction between a novel domain of the receptor Notch and the transcription factor RBP-J kappa/Su(H)

BACKGROUND

The mammalian transcription factor RBP-J kappa binds to the DNA sequence motif CGTGGGAA and is involved in the regulation of gene expression; for example, it plays a part in the transactivation of viral and cellular genes by Epstein-Barr virus nuclear antigen-2. The Drosophila homologue of RBP-J kappa is the product of the Suppressor of Hairless (Su(H)) gene. Su(H) is a neurogenic gene that acts downstream of Notch, which encodes a cell-surface receptor. Furthermore, in the mouse, the phenotypes of homozygous mutant Notch1 embryos are very similar to those of homozygous mutant RBP-J kappa embryos. Recent studies, using the yeast two-hybrid system, have led to the suggestion that the CDC10/ankyrin-like repeats of the Drosophila Notch protein interact with the Su(H) protein.

RESULTS

We searched for proteins that interact with mouse RBP-J kappa using the yeast two-hybrid system, and in this way identified a short intracellular region (mRAM23) of the mouse Notch1 protein that lacks any known sequence motif. In vitro interaction studies, using proteins fused to glutathione-S-transferase, showed that RBP-J kappa and Su(H) bind directly to the RAM23 regions of mouse Notch1 and Drosophila Notch, respectively. Immunoprecipitation analysis showed that RBP-J kappa and the mRAM23 region of mouse Notch1 also interact in vivo. Further studies, including site-directed mutagenesis experiments, narrowed down the region of mouse Notch1 that interacts with RBP-J kappa. The results indicate that this region is less than 50 amino-acid residues in length, and lies immediately downstream of the transmembrane region.

CONCLUSIONS

We show that the transcription factor RBP-J kappa/Su(H) interacts directly with a novel intracellular domain of the cell-surface receptor Notch. RBP-J kappa/Su(H) does not appear to interact with Notch via the CDC10/ankyrin repeats implicated in previous studies.

Recognition sequence of a highly conserved DNA binding protein RBP-J kappa

DNA binding specificity of the RBP-J kappa protein was extensively examined. The mouse RBP-J kappa protein was originally isolated as a nuclear protein binding to the J kappa type V(D)J recombination signal sequence which consisted of the conserved heptamer (CACTGTG) and nonamer (GGTTTTTGT) sequences separated by a 23-base pair spacer. Electrophoretic mobility shift assay using DNA probes with mutations in various parts of the J kappa recombination signal sequence showed that the RBP-J kappa protein recognized the sequence outside the recombination signal in addition to the heptamer but did not recognize the nonamer sequence and the spacer length at all. Database search identified the best naturally occurring binding motif (CACTGTGGGAACGG) for the RBP-J kappa protein in the promoter region of the m8 gene in the Enhancer of split gene cluster of Drosophila. The binding assay with a series of m8 motif mutants indicated that the protein recognized mostly the GTGGGAA sequence and also interacted weakly with ACT and CG sequences flanking this hepta-nucleotide. Oligonucleotides binding to the RBP-J kappa protein were enriched from a pool of synthetic oligonucleotides containing 20-base random sequences by the repeated electrophoretic mobility shift assay. The enriched oligomer shared a common sequence of CGTGGGAA. All these data indicate that the RBP-J kappa protein recognizes a unique core sequence of CGTGGGAA and does not bind to the V(D)J recombination signal without the flanking sequence.

Regulation of marginal zone B cell development by MINT, a suppressor of Notch/RBP-J signaling pathway

We found that Msx2-interacting nuclear target protein (MINT) competed with the intracellular region of Notch for binding to a DNA binding protein RBP-J and suppressed the transactivation activity of Notch signaling. Although MINT null mutant mice were embryonic lethal, MINT-deficient splenic B cells differentiated about three times more efficiently into marginal zone B cells with a concomitant reduction of follicular B cells. MINT is expressed in a cell-specific manner: high in follicular B cells and low in marginal zone B cells. Since Notch signaling directs differentiation of marginal zone B lymphocytes and suppresses that of follicular B lymphocytes in mouse spleen, the results indicate that high levels of MINT negatively regulate Notch signaling and block differentiation of precursor B cells into marginal zone B cells. MINT may serve as a functional homolog of Drosophila Hairless.

LIM protein KyoT2 negatively regulates transcription by association with the RBP-J DNA-binding protein

The RBP-J/Su(H) DNA-binding protein plays a key role in transcriptional regulation by targeting Epstein-Barr virus nuclear antigen 2 (EBNA2) and the intracellular portions of Notch receptors to specific promoters. Using the yeast two-hybrid system, we isolated a LIM-only protein, KyoT, which physically interacts with RBP-J. Differential splicing gave rise to two transcripts of the KyoT gene, KyoT1 and KyoT2, that encoded proteins with four and two LIM domains, respectively. With differential splicing resulting in deletion of an exon, KyoT2 lacked two LIM domains from the C terminus and had a frameshift in the last exon, creating the RBP-J-binding region in the C terminus. KyoT1 had a negligible level of interaction with RBP-J. Strong expression of KyoT mRNAs was detected in skeletal muscle and lung, with a predominance of KyoT1 mRNA. When expressed in F9 embryonal carcinoma cells, KyoT1 and KyoT2 were localized in the cytoplasm and the nucleus, respectively. The binding site of KyoT2 on RBP-J overlaps those of EBNA2 and Notchl but is distinct from that of Hairless, the negative regulator of RBP-J-mediated transcription in Drosophila. KyoT2 but not KyoT1 repressed the RBP-J-mediated transcriptional activation by EBNA2 and Notch1 by competing with them for binding to RBP-J and by dislocating RBP-J from DNA. KyoT2 is a novel negative regulatory molecule for RBP-J-mediated transcription in mammalian systems.

DRUNET: a dilated-residual U-Net deep learning network to segment optic nerve head tissues in optical coherence tomography images

Given that the neural and connective tissues of the optic nerve head (ONH) exhibit complex morphological changes with the development and progression of glaucoma, their simultaneous isolation from optical coherence tomography (OCT) images may be of great interest for the clinical diagnosis and management of this pathology. A deep learning algorithm (custom U-NET) was designed and trained to segment 6 ONH tissue layers by capturing both the local (tissue texture) and contextual information (spatial arrangement of tissues). The overall Dice coefficient (mean of all tissues) was 0.91 ± 0.05 when assessed against manual segmentations performed by an expert observer. Further, we automatically extracted six clinically relevant neural and connective tissue structural parameters from the segmented tissues. We offer here a robust segmentation framework that could also be extended to the 3D segmentation of the ONH tissues.

A Deep Learning System for Automated Angle-Closure Detection in Anterior Segment Optical Coherence Tomography Images

PURPOSE

Anterior segment optical coherence tomography (AS-OCT) provides an objective imaging modality for visually identifying anterior segment structures. An automated detection system could assist ophthalmologists in interpreting AS-OCT images for the presence of angle closure.

DESIGN

Development of an artificial intelligence automated detection system for the presence of angle closure.

METHODS

A deep learning system for automated angle-closure detection in AS-OCT images was developed, and this was compared with another automated angle-closure detection system based on quantitative features. A total of 4135 Visante AS-OCT images from 2113 subjects (8270 anterior chamber angle images with 7375 open-angle and 895 angle-closure) were examined. The deep learning angle-closure detection system for a 2-class classification problem was tested by 5-fold cross-validation. The deep learning system and the automated angle-closure detection system based on quantitative features were evaluated against clinicians' grading of AS-OCT images as the reference standard.

RESULTS

The area under the receiver operating characteristic curve of the system using quantitative features was 0.90 (95% confidence interval [CI] 0.891-0.914) with a sensitivity of 0.79 ± 0.037 and a specificity of 0.87 ± 0.009, while the area under the receiver operating characteristic curve of the deep learning system was 0.96 (95% CI 0.953-0.968) with a sensitivity of 0.90 ± 0.02 and a specificity of 0.92 ± 0.008, against clinicians' grading of AS-OCT images as the reference standard.

CONCLUSIONS

The results demonstrate the potential of the deep learning system for angle-closure detection in AS-OCT images.

Lamina cribrosa visibility using optical coherence tomography: comparison of devices and effects of image enhancement techniques

PURPOSE

To compare the visibility of the lamina cribrosa (LC) in optic disc images acquired from 60 glaucoma and 60 control subjects using three optical coherence tomography (OCT) devices, with and without enhanced depth imaging (EDI) and adaptive compensation (AC).

METHODS

A horizontal B-scan was acquired through the center of the disc using two spectral-domain (Spectralis and Cirrus; with and without EDI) and a swept-source (DRI) OCT. Adaptive compensation was applied post acquisition to improve image quality. To assess LC visibility, four masked observers graded the 1200 images in a randomized sequence. The anterior LC was graded from 0 to 4, the LC insertions from 0 to 2, and the posterior LC either 0 or 1. The effect of EDI, AC, glaucoma severity, and other clinical/demographic factors on LC visibility was assessed using generalized estimating equations.

RESULTS

The anterior LC was the most detectable feature, followed by the LC insertions. Adaptive compensation improved anterior LC visibility independent of EDI. Cirrus+EDI+AC generated the greatest anterior LC visibility grades (2.79/4). For LC insertions visibility, DRI+AC was the best method (1.10/2). Visibility of the posterior LC was consistently poor. Neither glaucoma severity nor clinical/demographic factors consistently affected LC visibility.

CONCLUSIONS

Adaptive compensation is superior to EDI in improving LC visibility. Visibility of the posterior LC remains poor suggesting impracticality in using LC thickness as a glaucoma biomarker.

A new primate from the Middle Eocene of Myanmar and the Asian early origin of anthropoids

A new genus and species of anthropoid primate, Bahinia pondaungensis gen. et sp. nov., is described from the Yashe Kyitchaung locality in the Late Middle Eocene Pondaung Formation (Myanmar). It is related to Eosimias, but it is represented by more complete remains, including upper dentition with associated lower jaw fragment. It is interpreted as a new representative of the family Eosimiidae, which corresponds to the sister group of the Amphipithecidae and of all other anthropoids. Eosimiidae are now recorded from three distinct Middle Eocene localities in Asia, giving support to the hypothesis of an Asian origin of anthropoids.

A lower jaw of Pondaungia cotteri from the Late Middle Eocene Pondaung Formation (Myanmar) confirms its anthropoid status

Pondaungia cotteri is the largest primate known from the Late Middle Eocene Pondaung Formation, Myanmar. Its taxonomic status has been the subject of much debate because of the fragmentary nature of its remains. Initially described as an anthropoid, some authors recently have associated it with adapid primates. These debates have been fueled not only by the incompleteness of the fossils attributed to Pondaungia but also by the reticence of many authors to regard Asia as an important evolutionary theater for Eocene anthropoids. During the November 1998 Myanmar-French Pondaung Expedition, a right lower jaw was discovered that yields the most nearly complete dentition of Pondaungia cotteri ever found: it shows the complete horizontal ramus, alveoli for the second incisor and canine, three premolars, and three molars. The symphysis showed all characteristics of anthropoids but was unfused. The canine root is large, the first premolar is absent, and the second premolar is single-rooted, reduced, and oblique in the tooth row, as in anthropoids. The premolars show a reduced mesio-distal length compared with the tooth row, and their morphology is very similar to that of Amphipithecus mogaungensis. Therefore, the two Pondaung taxa appear to be closely related to each other, with Siamopithecus as their sister taxon.

A Deep Learning Approach to Denoise Optical Coherence Tomography Images of the Optic Nerve Head

Optical coherence tomography (OCT) has become an established clinical routine for the in vivo imaging of the optic nerve head (ONH) tissues, that is crucial in the diagnosis and management of various ocular and neuro-ocular pathologies. However, the presence of speckle noise affects the quality of OCT images and its interpretation. Although recent frame-averaging techniques have shown to enhance OCT image quality, they require longer scanning durations, resulting in patient discomfort. Using a custom deep learning network trained with 2,328 'clean B-scans' (multi-frame B-scans; signal averaged), and their corresponding 'noisy B-scans' (clean B-scans + Gaussian noise), we were able to successfully denoise 1,552 unseen single-frame (without signal averaging) B-scans. The denoised B-scans were qualitatively similar to their corresponding multi-frame B-scans, with enhanced visibility of the ONH tissues. The mean signal to noise ratio (SNR) increased from 4.02 ± 0.68 dB (single-frame) to 8.14 ± 1.03 dB (denoised). For all the ONH tissues, the mean contrast to noise ratio (CNR) increased from 3.50 ± 0.56 (single-frame) to 7.63 ± 1.81 (denoised). The mean structural similarity index (MSSIM) increased from 0.13 ± 0.02 (single frame) to 0.65 ± 0.03 (denoised) when compared with the corresponding multi-frame B-scans. Our deep learning algorithm can denoise a single-frame OCT B-scan of the ONH in under 20 ms, thus offering a framework to obtain superior quality OCT B-scans with reduced scanning times and minimal patient discomfort.

Loss of Viral Control in Early HIV‐1 Infection Is Temporally Associated with Sequential Escape from CD8+T Cell Responses and Decrease in HIV–1–Specific CD4+and CD8+T Cell Frequencies

The outcome of human immunodeficiency virus type 1 (HIV-1) infection is related to the set-point plasma virus load (pVL) that emerges after primary HIV-1 infection (PHI). This set-point pVL generally remains stable but eventually increases with progression to disease. However, the events leading to loss of viremic control are poorly understood. Here, we describe an individual who presented with symptomatic PHI and subsequently progressed rapidly, after an initial period of 1 year during which viral replication was well controlled. Escalation of viral replication in this atypical case was preceded by the emergence of escape variants in many epitopes targeted by dominant CD8+ T cell responses and a marked decrease in HIV-1-specific CD4+ and CD8+ T cell frequencies. There were no changes in viral tropism, replication kinetics, or neutralizing antibody titers. These findings demonstrate the temporal relationship between viral escape from CD8+ T cell activity, decrease in HIV-1-specific T cell frequencies, and loss of control of viral replication.

Novel anterior-chamber angle measurements by high-definition optical coherence tomography using the Schwalbe line as the landmark

OBJECTIVE

To propose the Schwalbe line (SL) as a new anatomical landmark, independent of the scleral spur (SS) location, for assessing anterior chamber angle (ACA) width quantitatively with high-definition optical coherence tomography (HD-OCT).

METHODS

Study subjects underwent dark-room gonioscopy and HD-OCT in one randomly selected eye. The authors developed a computer-aided program to define two new quantitative parameters for assessing ACA width: Schwalbe line-angle opening distance (SL-AOD) measured at the SL, and Schwalbe line-trabecular-iris space area (SL-TISA) measured 500 μm from the SL. The associations between SL parameters, SS parameters and gonioscopic grading were evaluated.

RESULTS

Seventy-three (47 females, 26 males) subjects were recruited, the majority of whom were Chinese (89%). The authors excluded 29 images (19.9%) owing to poor image quality, leaving 117 HD-OCT images (65 nasal, 52 temporal) for analysis. SL and SS could be identified in 95% and 85% of quadrants respectively (p = 0.035). SL-AOD and SL-TISA were significantly correlated with SS parameters (all r ≥ 0.85) and gonioscopic grading (all r ≥ 0.69). In eyes with closed angles (n = 36), SL parameters showed strong correlations with gonioscopic grading (r ranged from 0.43 to 0.44). Conclusions Novel angle parameters, based on SL as a landmark, may be useful to quantify ACA width and to assess for risk of angle closure.

A newly developed three-layer agarose microcapsule for a promising biohybrid artificial pancreas: rat to mouse xenotransplantation

We examined the effectiveness of an improved version of a three-layer agarose microcapsule in islet xenotransplantation. The microcapsule is composed of a mixture of 5% agarose and 5% polystyrene sulfonic acid. The other two outer layers are polybrene and carboxymethyl cellulose. The agarose/polystyrene sulfonic acid membrane is for the purpose of immunoisolation, suppression of complement activity and reinforcement of the microcapsule. The polybrene layer suppresses the polystyrene sulfonic acid leakage by forming a polyionic complex at the surface of the agarose/polystyrene sulfonic acid membrane. The outermost layer, a carboxymethyl cellulose coating, improves the biocompatibility of the microcapsule. In vitro static incubation study showed that the insulin secretion from rat islets in microcapsules in response to 16.7 mM glucose stimulation was more than four times higher than that on 3.3 mM glucose stimulation (n = 8). In an in vivo study, 500 rat islets in microcapsules were xenogenically implanted in the abdominal cavity of mice with streptozotocin-induced diabetes. The graft survival times ranged from 2 to 5 mo, the average being 75 days (n = 5). Our results demonstrate that the improved version of the three-layer agarose microcapsule can effectively prolong the xenograft survival time without employing immunosuppressants, suggesting that this microcapsule could provide a promising biohybrid artificial pancreas for future clinical applications.

Swept source optical coherence tomography measurement of the iris-trabecular contact (ITC) index: a new parameter for angle closure

PURPOSE

To evaluate the inter- and intra-observer agreement of measurement of the iris-trabecular contact (ITC) index, a measure of the degree of angle closure, using swept source optical coherence tomography (SSOCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan).

METHODS

One randomly selected eye of 60 subjects was imaged under dark room conditions. The SSOCT 3-dimensional angle scan simultaneously obtains 128 radial scans of the anterior chamber for the entire circumference of the angle. Post-imaging analysis estimated the ITC index using in-built software. For intra-observer agreement for image grading, one examiner performed the grading twice in a masked fashion and random order after a 1-week interval. A second examiner graded images to assess inter-observer agreement for image grading. For intra-observer agreement for image acquisition, a single operator imaged patients twice. For inter-observer agreement for image acquisition, a single observer graded two sets of images acquired by two different operators on the same patient. Bland-Altman plots and 95 % limits of agreement (LOA) were reported.

RESULTS

Study subjects were predominantly Chinese (54/60, 90 %) and female (42/60, 70 %), with a mean age of 65.5 years. The median ITC index for eyes with open angles (31/60) and closed angles was 20 % (95 % confidence interval [CI] - 13.6, 27.8) and 49 % (95%CI - 35.5, 69.2) respectively. The mean difference (95 % LOA) for intra-observer agreement for image grading and image acquisition were -0.8 % (-8.2, 6.5) and 0.6 % (-10.9, 9.7); corresponding inter- observer agreement were 0.1 % (-10, 10.1) and -0.3 % (-11.1, 10.5) respectively.

CONCLUSIONS

The inter- and intra-observer agreement of the ITC index, as a measure of extent of angle closure using SSOCT, was good.

Assessment of trabecular meshwork width using swept source optical coherence tomography

PURPOSE

Measurements of the angle width by ultrasound biomicroscopy or anterior segment optical coherence tomography are usually performed 500 μm from the scleral spur, as the anterior part of trabecular meshwork (TM) is assumed to lie within this distance. The aim of this study was to measure TM width using swept source optical coherence tomography (SS-OCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan), and to investigate factors influencing this measurement.

METHODS

Participants underwent gonioscopy and SS-OCT imaging in the dark. High-definition SS-OCT images were corrected for refractive distortion; and customized software (ImageJ; National Institutes of Health, Bethesda, MD, USA) was utilized to measure TM width (distance between the scleral spur and Schwalbe's line). Linear regression analysis was performed to assess the relationship between TM width with demographic and angle parameters.

RESULTS

One hundred and forty eight Chinese subjects were analyzed. The majority was female (62.4 %); the mean age was 59.2 ± 8.68 years. Identification of the scleral spur and Schwalbe's line with SS-OCT was possible in 590 (99.7 %) and 585 angle quadrants (98.8 %) respectively. TM width was wider in the inferior and superior quadrants (mean 889 [SD 138] and 793 [136] μm), compared to the nasal and temporal quadrants (712 [137] and 724 [115] μm, P<0.001). There was a difference in average TM width between open (789 [100]) and closed angle eyes (753 [86]) (P=0.048). There was no significant association between TM width and angle parameters, laterality, or demographic factors.

CONCLUSIONS

In SS-OCT HD images, the mean TM width varied from 710 to 890 μm in the different quadrants of the eye, and the inferior quadrant TM was the widest compared to other quadrants.

Mechanisms of hearing loss in acoustic neuroma: an otoacoustic emission study

Evoked otoacoustic emissions (EOAE) are active mechanical responses from the cochlea which provide information about the integrity of the preneural cochlear receptor mechanisms. It may be hypothesised, therefore, that if a hearing impairment is neural in origin, normal EOAEs may be obtained from the cochlea, which, although dissociated, is functioning normally. This study examined the status of the cochlea with EOAE in patients with cochlear (Meniere's disease) and neural (surgically proven acoustic neuroma) disease. In patients with presumed cochlear lesions, no emissions were present with mean hearing worse than 40 dB across a frequency range of 0.5 to 4 kHz. Similarly, an EOAE was not present in any of the 26 acoustic neuroma patients studied when the average (0.5 to 4 kHz) hearing was greater than 40 dB. We conclude that dissociation of the cochlea in patients with acoustic neuroma appears to be rare and, in fact, cochlear involvement occurs in most cases. Possible mechanisms responsible for the effect on the cochlea in this group include degenerative changes due to chronic partial obstruction of the blood supply by the tumour, biochemical alterations in the inner ear fluids, loss of efferent control of active mechanical tuning, and hair cell degeneration secondary to neuronal loss in the eighth nerve.

In Vivo Three-Dimensional Lamina Cribrosa Strains in Healthy, Ocular Hypertensive, and Glaucoma Eyes Following Acute Intraocular Pressure Elevation

Purpose

To compare in vivo lamina cribrosa (LC) strains (deformations) following acute IOP elevation in healthy, glaucoma, and ocular hypertensive subjects.

Methods

There were 20 healthy, 20 high-tension primary open-angle glaucoma (POAG), 16 primary angle-closure glaucoma (PACG), and 20 ocular hypertensive (OHT; with normal visual fields) eyes studied. For each test eye, the optic nerve head was imaged three times (at baseline IOP, following an acute elevation of IOP to approximately 35 then 45 mm Hg using an ophthalmodynamomter) using optical coherence tomography (OCT). A three-dimensional (3D) strain-mapping algorithm was applied to both sets of baseline and IOP-elevated OCT volumes to extract IOP-induced 3D strains. Octant-wise LC strains were also extracted to study the pattern of local deformation.

Results

The average LC strain in OHT subjects (3.96%) was significantly lower than that measured in healthy subjects (6.81%; P < 0.05). On average, POAG subjects experienced higher strain than the PACG subjects (4.05%), healthy subjects experienced higher strains than the POAG and PACG subjects, but these difference were not statistically significant. Local LC deformations showed lowest strain in the infero-temporal and temporal octant in the POAG and OHT subjects.

Conclusions

We demonstrate measurable LC strains in vivo in humans as a response to acute IOP elevation. In this population, our data suggest that OHT LCs experience lower IOP-induced strains than healthy LCs.

Variations in iris volume with physiologic mydriasis in subtypes of primary angle closure glaucoma

PURPOSE

To compare the changes in iris volume with pupil dilation using anterior segment optical coherence tomography (AS-OCT) in eyes of subjects with different subtypes of primary angle closure.

METHODS

This prospective study examined 44 fellow eyes (FA group) of subjects with previous acute primary angle closure (APAC), and 56 subjects (AC group) with chronic primary angle closure and/or primary angle closure glaucoma. All participants underwent gonioscopy and AS-OCT imaging. The iris volume, iris cross-sectional area, and pupil diameter were measured with custom semiautomated software. The main outcome variable analyzed was mean change in iris volume between light and dark conditions in a multivariate linear regression analysis.

RESULTS

Thirty-five eyes from the FA group (79.5%) and 50 eyes from the AC group (89.3%) were included in the final analysis. When going from light to dark, iris volume did not change significantly in eyes in the FA group (+1.50 ± 6.73 mm(3); P = 0.19), but decreased in the AC group by 1.52 ± 3.07 mm(3) (P < 0.001). This difference was significant (P = 0.01). On multivariate analysis after controlling for age, sex, baseline pupil diameter, and change in pupil diameter, age (β = -0.397; P < 0.001) and diagnostic category (AC versus FA group; β = 0.347; P < 0.001) were significant determinants of iris volume change.

CONCLUSIONS

With physiologic mydriasis, the iris volume decreased in eyes with chronic angle closure but remained unchanged in fellow eyes of APAC. Such variations in iris volume responses may influence the subtype of angle closure that develops.

Effects of endothelin on microcirculation of the pancreas

Endothelin, a newly described endothelial-derived peptide, has potent vasoconstrictive properties and has been speculated to play a physiological role in the regulation of blood flow in some organs. The present study was designed to evaluate the effects of endothelin-1, endothelin-2 and endothelin-3 on the pancreatic microcirculation. Pancreatic tissue blood flow was measured by a laser Doppler flow meter in anesthetized dogs and endothelin-1, endothelin-2 or endothelin-3 was injected intravenously in graduated doses. Endothelins induced dose-dependent decreases in pancreatic tissue blood flow. Endothelin-1, endothelin-2 and endothelin-3 at a dose of 100 pmol/kg reduced pancreatic blood flow by 45.4%, 19.6% and 51.9%, respectively, whereas systemic arterial blood pressure was not significantly affected. When endothelin-3 was administered at a dose of 1000 pmol/kg, pancreatic blood flow was decreased by 73.5% with a concomitant increase of systemic arterial blood pressure by 17.6%. Endothelins potently decreased pancreatic tissue blood flow, suggesting a possible role of these agents in regulating the pancreatic microcirculation.

Determinants of optical coherence tomography-derived minimum neuroretinal rim width in a normal Chinese population

PURPOSE

To characterize an optical coherence tomography (OCT)-derived parameter, Bruch's membrane opening-minimum rim width (BMO-MRW), and its association with demographic and clinical parameters in normal Chinese subjects.

METHODS

Right eyes of 466 consecutive healthy subjects from a population-based study of Singaporean Chinese underwent Cirrus OCT imaging. The retinal internal limiting membrane (ILM) and BMO were automatically delineated using the built-in Cirrus algorithm. The standard 36 interpolated radial B-scans (72 BMO points, 5° increments) of each optic nerve head were manually extracted from the central circle (3.46-mm diameter). We used Matlab to measure the shortest distance from the BMO points to the ILM. Associations of BMO-MRW with demographic and clinical parameters were evaluated using marginal general estimating equations analysis.

RESULTS

There was a slight preponderance of male subjects (50.9%), with a mean age of 54.8 ± 7.63 years. Mean BMO-MRW was 304.67 ± 58.96 μm (range, 173.32-529.23 μm), which was highly associated with OCT-derived disc area (DA) (β = -91.78, P < 0.001) and rim area (RA) (β = 194.31, P < 0.001), followed by spherical refractive error (SRE) (β = -2.23, P = 0.02) and retinal nerve fiber layer (RNFL) thickness (β = 0.5, P = 0.04), after adjusting for the associated factors such as age, sex, intraocular pressure (IOP), and vertical cup-disc ratio (VCDR).

CONCLUSIONS

Disc area and RA had the strongest association with BMO-MRW, followed by SRE and RNFL thickness. The availability of this normative database will facilitate optic nerve head assessment using the BMO-MRW parameter in Chinese subjects.

Comparison of two spectral domain optical coherence tomography devices for angle-closure assessment

PURPOSE

To compare two spectral domain optical coherence tomography (SD-OCT) devices for the identification of angle structures and the presence of angle closure.

METHODS

This was a prospective comparative study. Consecutive patients underwent gonioscopy and anterior segment imaging using two SD-OCT devices (iVue and Cirrus). Images were evaluated for the ability to detect angle structures such as Schwalbe's line (SL), trabecular meshwork (TM), Schlemm's canal (SC), and scleral spur (SS), and the presence of angle closure. Angle closure was defined as iris contact with the angle wall anterior to the SS on SD-OCT, and nonvisibility of the posterior TM on gonioscopy. Angle closure in an eye was defined as ≥two quadrants of closed angles. AC1 statistic was used to assess the agreement between devices.

RESULTS

Of the 69 subjects studied (46.4% male, 84.1% Chinese, mean age 64.0 ± 10.5 years), 40 subjects (40 eyes, 58.0%) had angle closure on gonioscopy. The most identifiable structure on Cirrus SD-OCT was the SS (82.2%) and SL on iVue SD-OCT (74.5%). Angle closure was indeterminable in 14.5% and 50.7% of Cirrus and iVue scans (P < 0.001), respectively. Interdevice agreement for angle closure was moderately strong (AC1 = 0.67), but agreement with gonioscopy was only fair (AC1 = 0.35 and 0.50 for Cirrus and iVue, respectively).

CONCLUSIONS

It was more difficult to determine angle closure status with iVue compared with Cirrus SD-OCT. There was fair agreement between both devices with gonioscopy for identifying angle closure.

Shape Changes of the Anterior Lamina Cribrosa in Normal, Ocular Hypertensive, and Glaucomatous Eyes Following Acute Intraocular Pressure Elevation

Purpose

The purpose of this study was to estimate and compare changes in anterior lamina cribrosa (LC) morphology in normal, ocular hypertensive (OHT), and glaucomatous eyes following acute elevations in intraocular pressure (IOP).

Methods

The optic nerve heads (ONHs) of 97 subjects (17 OHT, 19 primary open-angle glaucoma [POAG], 31 primary angle-closure glaucoma [PACG], and 30 normal subjects) were imaged using optical coherence tomography (OCT). Intraocular pressure was raised twice by applying forces to the anterior sclera, using an ophthalmodynamometer. After each IOP elevation, IOP was held constant and measured; each ONH was rescanned with OCT. In each OCT volume, the anterior LC was enhanced, delineated, and its global shape index (GSI) calculated and compared across groups.

Results

The baseline IOP was 17.5 ± 3.5 mm Hg and was increased to 38 ± 5.9 mm Hg and then to 46.5 ± 5.9 mm Hg. At the first IOP increment, mean GSI was significantly smaller than that at baseline in normal subjects and glaucoma subjects (P < 0.05) but not in OHT subjects (P = 0.12). For the second IOP increment, the mean GSI was significantly smaller than that at baseline in normal subjects and in OHT eyes (P < 0.05). After adjusting for age, sex, and baseline IOP, the LC of POAG eyes was found to be significantly more posteriorly curved than that of normal subjects (P = 0.04).

Conclusions

Acute IOP elevations altered anterior LC shape in a complex nonlinear fashion. The LC of POAG eyes was more cupped following acute IOP elevations compared to that of normal subjects.

Understanding diagnostic disagreement in angle closure assessment between anterior segment optical coherence tomography and gonioscopy

BACKGROUND/AIMS

Although being a more objective tool for assessment and follow-up of angle closure, reliability studies have reported a moderate diagnostic performance for anterior segment optical coherence tomography (OCT) technologies when comparing with gonioscopy as the reference standard. We aim to determine factors associated with diagnostic disagreement in angle closure when assessed by anterior segment swept source OCT (SS-OCT, CASIA SS-1000; Tomey, Nagoya, Japan) and gonioscopy.

METHODS

Cross-sectional study. A total of 2027 phakic subjects aged ≥50 years, with no relevant previous ophthalmic history, were consecutively recruited from a community polyclinic in Singapore. Gonioscopy and SS-OCT (128 radial scans) for the entire circumference of the angle were performed for each subject. A two-quadrant closed gonioscopic definition was used. On SS-OCT images, angle closure was defined as iridotrabecular contact (ITC) to the extent of ≥35%, ≥50% and ≥75% of the circumferential angle. Diagnostic disagreements between both methods, that is, false positives or overcalls and false negatives or undercalls were defined, respectively, as gonioscopic open/closed angles inversely assessed as closed/open by SS-OCT.

RESULTS

Two hundred and seventy-two (14.7%) resulted in overcall results (false positives) when ≥50% of the angle circumference was closed using SS-OCT. These eyes had significantly wider (anterior chamber width, 11.7 vs 11.6 mm, p<0.001) and deeper (anterior chamber depth (ACD), 2.4 vs 2.2 mm, p<0.001) anterior chambers than eyes assessed by both methods as closed (true positives). Deeper ACD (OR 9.31) and lower lens vault (LV) (OR 0.04) were significantly associated with a false positive diagnosis in the multivariate analysis. Most of these cases had short (52.6%) or irregular (39%) ITC in SS-OCT images.

CONCLUSIONS

We found that anterior chamber dimensions, determined by ACD and LV, were factors significantly associated with diagnostic disagreement between anterior segment SS-OCT and gonioscopy in angle closure assessment.