Periodic Stratification of Colloids in a Liquid Phase Produced by a Precipitation Reaction and Gel Swelling.

Pattern formation is a frequent phenomenon occurring in animate and inanimate systems. The interplay between the mass transport of the chemical species and the underlying chemical reaction networks generates most patterns in chemical systems. Periodic precipitation is an emblematic example of reaction-diffusion patterns, in which the process generates a spatial periodic structure in porous media. Here, we use the dormant reagent method to produce colloidal particles of Prussian blue (PB) and PB analogues at the liquid-gel interface. The generated particles produced a stable periodic stratification pattern in time in the liquid phase placed on top of the solid hydrogel. The phenomenon is governed by periodic swelling of the gel driven by the osmotic stress and stability of the formed particles. To illustrate the phenomenon, we developed an extended reaction-diffusion model, which incorporated the gel swelling and sedimentation effect of the formed colloids and could qualitatively reproduce the pattern formation in the liquid phase.

MERCURY-3: a randomized comparison of netarsudil/latanoprost and bimatoprost/timolol in open-angle glaucoma and ocular hypertension.

PURPOSE   : To compare the efficacy and safety of the fixed-dose combination (FDC) of netarsudil 0.02%/latanoprost 0.005% ophthalmic solution (NET/LAT; Roclanda®) with bimatoprost 0.03%/timolol maleate 0.5% (BIM/TIM; Ganfort®) ophthalmic solution in the treatment of open-angle glaucoma (OAG) and ocular hypertension (OHT). METHODS: MERCURY-3 was a 6-month prospective, double-masked, randomized, multicenter, active-controlled, parallel-group, non-inferiority study. Patients (≥ 18 years) with a diagnosis of OAG or OHT in both eyes that was insufficiently controlled with topical medication (IOP ≥ 17 mmHg in ≥ 1 eye and < 28 mmHg in both eyes) were included. Following washout, patients were randomized to once-daily NET/LAT or BIM/TIM for up to 6 months; efficacy was assessed at Week 2, Week 4, and Month 3; safety was evaluated for 6 months. Comparison of NET/LAT relative to BIM/TIM for mean IOP at 08:00, 10:00, and 16:00 h was assessed at Week 2, Week 6, and Month 3. Non-inferiority of NET/LAT to BIM/TIM was defined as a difference of ≤ 1.5 mmHg at all nine time points through Month 3 and ≤ 1.0 mmHg at five or more of nine time points through Month 3. RESULTS: Overall, 430 patients were randomized (NET/LAT, n = 218; BIM/TIM, n = 212), and all received at least one dose of study medication. Efficacy analyses were performed at Month 3 on 388 patients (NET/LAT, n = 184; BIM/TIM, n = 204). NET/LAT demonstrated non-inferiority to BIM/TIM, with a between-treatment difference in IOP of ≤ 1.5 mmHg achieved at all time points and ≤ 1.0 mmHg at the majority of time points (six of nine) through Month 3. Mean diurnal IOP during the study ranged from 15.4 to 15.6 mmHg and 15.2 to 15.6 mmHg in the NET/LAT and BIM/TIM groups respectively, with no between-group statistically significant difference. No significant differences were observed in key secondary endpoints. No serious, treatment-related adverse events (AEs) were observed, and AEs were typically mild/moderate in severity. The most common treatment-related AEs were conjunctival hyperemia (NET/LAT, 30.7%; BIM/TIM, 9.0%) and cornea verticillata (NET/LAT, 11.0%; BIM/TIM, 0%). CONCLUSIONS: Once-daily NET/LAT was non-inferior to BIM/TIM in IOP reduction in OAG and OHT, with AEs consistent with previous findings. NET/LAT offers a compelling alternative FDC treatment option for OAG and OHT.

A Dormant Reagent Reaction-Diffusion Method for the Generation of Co-Fe Prussian Blue Analogue Periodic Precipitate Particle Libraries.

Liesegang patterns that develop as a result of reaction-diffusion can simultaneously form products with slightly different sizes spatially separated in a single medium. We show here a reaction-diffusion method using a dormant reagent (citrate) for developing Liesegang patterns of cobalt hexacyanoferrate Prussian Blue analog (PBA) particle libraries. This method slows the precipitation reaction and produces different-sized particles in a gel medium at different locations. The gel-embedded particles are still catalytically active. Finally, the applicability of the new method to other PBAs and 2D systems is presented. The method proves promising for obtaining similar inorganic framework libraries with catalytic abilities.

Bioinspired Control of Calcium Phosphate Liesegang Patterns Using Anionic Polyelectrolytes.

The Liesegang phenomenon is a spontaneous pattern formation, which is a periodic distribution of the precipitate discovered in diffusion-limited systems. Over the past century, it has been experimentally attempted to control the periodicity of patterns and structures of precipitates by varying the concentration of the hydrogel or electrolytes, adding organic or inorganic impurities, and applying an electric or pH field. In this work, the periodic patterns of calcium phosphate were manipulated with an anionic macromolecular additive inspired by bone mineralization in which various noncollagenous proteins are involved in the formation of a polymer-induced liquid precursor. The periodic patterns were systematically controlled by adjusting the amount of poly(acrylic acid), and they were numerically simulated by adjusting the threshold concentration of nucleation. The change of the pattern is explained by improved stability and directional diffusion of the intermediate.

Shape changes and budding of giant vesicles induced by an internal chemical trigger: an interplay between osmosis and pH change.

Shape transformation and budding of phospholipid/fatty acid giant hybrid vesicles can be induced by an internal chemical stimulus (pH change) when coupled with an osmotic shock. In particular, an autocatalytic enzymatic reaction set (urea-urease system), confined in the lumen of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/oleic acid (HOA) vesicles, can force the budding of the hosting vesicle, when properly fed by a trans-membrane substrate infusion. Herein, we elucidate the budding mechanism by simulating the shape changes of a vesicle during the enzymatic reaction. The area-difference-elasticity (ADE) theory is thus implemented to minimize the surface elastic energy and obtain the equilibrium shape at different values of the reduced volume and different values of the reduced preferred area difference (Δa0). Simulations, together with control experiments, unambiguously show that to obtain an effective vesicle shape transformation, the osmotic stress and the pH change in the lumen of the vesicle must act in synergy at the same timescale. Osmotic pressure induces a vesicle deflation (volume loss), while the pH change affects the preferred area difference between the outer and the inner membrane leaflets.

Influence of painless one-eye blindness on depression, anxiety and quality of life in glaucoma patients with a normal fellow eye.

BACKGROUND: For clinical practice it is important to evaluate and compare anxiety, depression and quality of life of glaucoma patients with painless one-eye blindness and a normal fellow eye to unaffected age-matched individuals from a similar environment. METHODS: Twenty-eight stable glaucoma patients (age, mean ± SD: 69.0 ± 13.3 years) with one normal and one painless blind eye, and 26 controls (age: 67.0 ± 14.0 years) completed the standard Hungarian adaptations of the Beck Depression Inventory, Beck Anxiety Inventory, Spielberger-Trait Anxiety Inventory, Hopelessness Scale, and Quality of Life Questionnaire SF-36 with the assistance of trained psychologist interviewers within 3 months after a detailed ophthalmological examination. RESULTS: The groups did not differ in age, gender distribution, number of children, grandchildren and people in their household (p ≥ 0.235). The best corrected visual acuity (BCVA) of the diseased eye was minimal (median: 0.00), while BCVA of their better eye (median: 1.0) did not differ from that of the control group (p ≥ 0.694). Compared to the control group, the patients' scores were significantly higher for depression (p ≤ 0.01), cognitive and psychophysiological symptoms of anxiety (p ≤ 0.05) and hopelessness (p ≤ 0.013), and lower (worse) for physical function, vitality, general health and bodily pain (p ≤ 0.045). No difference was found between the groups for mental health, physical role functioning, emotional role functioning and social role functioning (p ≥ 0.117). CONCLUSION: Our results show that patients with glaucoma-related one-eye blindness may require regular psychological support even when the visual performance of the fellow eye is fully maintained on the long run, and the patients' everyday functioning is normal.

Carbon Dioxide-Driven Coupling in a Two-Compartment System: Methyl Red Oscillator.

Strategies for designing autonomous oscillatory systems have gained much attention in the past few decades. A broadly accepted and used strategy for the generation of forced oscillations in the originally non-oscillatory subsystems is to couple a pH (driving) oscillator to a pH-sensitive substance (forced oscillatory subsystem) in a one-compartment system. The forced oscillatory subsystem comprises pH-sensitive components, which inevitably generate negative feedback and affect the characteristics of the driving oscillatory system. Here, we present a different approach by separating the driving and forced oscillatory systems into a two-compartment system using a silicone membrane, and the forced oscillations of the absorbance of a pH-sensitive chemical species (methyl red dye) were realized by the transport of carbon dioxide through the membrane generated periodically by the driving pH oscillator. The transported carbon dioxide produced the pH change in the separated compartment by carbon dioxide-hydrogen carbonate-carbonate equilibria and created forced oscillations of a pH-sensitive chemical species manifested in the oscillation of its absorbance at a fixed wavelength. This approach avoids any feedback from the forced oscillatory system to the driving system via the cross-membrane transport of the chemical species from the forced to the driving oscillatory system. Additionally, we present that this carbon dioxide coupling to the methyl red dye can be used to estimate the carbon dioxide content in both liquid and gas phases.

Real-life experience of using brinzolamide/brimonidine fixed drop combination in a tertiary glaucoma centre.

PURPOSE: To investigate the intraocular pressure (IOP)-lowering efficacy and tolerance of brinzolamide/brimonidine fixed combination (BBFC) under real-life conditions in a tertiary glaucoma centre. METHODS: Medical records of all ocular hypertensive and open-angle glaucoma patients (n = 52) treated with BBFC were retrospectively analysed. RESULTS: Thirty-nine patients had primary open-angle, 6 exfoliative, 2 pigment, 1 normal tension and 1 juvenile open-angle glaucoma and 3 ocular hypertension. The prior therapy was a prostaglandin analogue (PG) (n = 4), PG/timolol (n = 20), PG/timolol and topical carbonic anhydrase inhibitor (CAI; n = 19), timolol/CAI (n = 1), PG and CAI (n = 4), timolol/pilocarpine and PG (n = 1), timolol/brimonidine and PG (n = 1) and timolol/brimonidine, PG and CAI (n = 2). These were simplified to PG/timolol and BBFC (n = 41), PG and BBFC (n = 9), timolol and BBFC (n = 1) and timolol/pilocarpine, PG and BBFC (n = 1). The IOP on the study eyes was 21.2 ± 3.7 mmHg before and 16.9 ± 2.6, 16.0 ± 2.2, 17.6 ± 3.1 and 18.0 ± 3.1 mmHg after the introduction of BBFC at month 1, 3, 6 and 12, respectively (p < 0.0003 for all time points compared to baseline, p = 1.0 for all other comparisons). Thirty-one patients (59.6%) experienced no adverse event, 17 (32.7%) reported ocular and 6 (11.5%) systemic adverse events. BBFC therapy was terminated on 27 patients (51.9%): on 19 (36.5%) due to adverse events and on 8 (15.4%) due to insufficient IOP reduction. CONCLUSION: In real-life practice, the introduction of BBCF allows significant and clinically meaningful IOP reduction and therapy simplification in glaucoma patients requiring complex medication, but in more than one third of the patients it is not tolerated due to adverse events.

Nanocrystals Assembled by the Chemical Reaction of the Dispersion Solvent.

The development of methods to pattern nanocrystals with different sizes and shapes remains a challenge. In this study, we demonstrate a unique class of bottom-up approaches to assemble nanocrystals into patterns. Our approach for patterning nanocrystals focuses on the utilization and control of the chemical reaction of solvents surrounding nanocrystals. The photopolymerization of solvent molecules through a photomask creates time-dependent concentration gradients of the solvents. Dispersed nanocrystals such as silver nanowires (AgNWs) migrate and are gradually organized and integrated into the polymerizing films based on the concentration gradients. The AgNW-embedded film properties are determined by the organized AgNW structures and include light transmission and electrical conductivity. Overall, the demonstrated method is very simple, widely applicable to various nanocrystals and solvents, and can thus contribute to the development of a new class of nanocrystal patterning methods.

Autonomous Chemical Modulation and Unidirectional Coupling in Two Oscillatory Chemical Systems.

Controlling and coupling of out-of-equilibrium reaction networks have great importance in chemistry and biology. We provide an example for the ideal master-slave coupling between two pH oscillators (the sulfite-bromate and the hydrogen peroxide-sulfite pH oscillators operated in continuous-flow stirred tank reactors). The coupling between the reactors was realized by transport of carbon dioxide through a silicon membrane, which is a common chemical species in both systems. We showed that by using this strategy, the master system can generate forced pH oscillations in the slave system. We could control the amplitude and frequency of the oscillations in the slave system and reversibly drive the transition in the oscillations between the regular and chaotic regimes. Using this coupling strategy, we could present an example of amplitude modulation in a coupled chemical system.

Peripapillary capillary vessel density progression in advanced glaucoma: a case report.

BACKGROUND: We report a case of advanced juvenile open-angle glaucoma (JOAG) in which peripapillary capillary vessel density (PcVD) in the inferior retina showed significant progression while the spatially corresponding retinal nerve fiber layer thickness (RNFLT) and visual field cluster defect values had reached their minimal detectable values, and showed no change during the follow-up (floor effect). CASE PRESENTATION: A 45-year old white female patient with very advanced under treatment JOAG in the left eye was prospectively investigated with the AngioVue OCT (Optovue Inc., Fremont, USA) for RNFLT and PcVD, and Octopus Normal G2 visual field testing, at 6-month intervals for 2.5 years (6 visits). Images quality was high (8/10 in 5 visits and 7/10 in one visit), and the optical media were clear. For the superior and inferior retina the baseline RNFLT and PcVD values were 48 and 43 µm, and 28.9 and 36.5%, respectively. Using the instrument's linear regression analysis significant progression (P < 0.05) was seen only for the hemifield with greater baseline RNFLT (superior RNFLT: - 0.5 µm/year) and the hemifield with greater baseline PcVD (inferior PcVD: - 2.4%/year). All inferior visual field cluster defect values progressed significantly (2.0 to 5.1 dB/year) while in the superior clusters no progression was measurable due to software indicated floor effect. CONCLUSION: Our case shows that PcVD progression can be measured in advanced glaucoma, that PcVD can show floor effect, and that it may indicate glaucomatous progression when the spatially corresponding RNFLT and visual field cluster defect do not show progression due to floor effect.

Existence of a Precipitation Threshold in the Electrostatic Precipitation of Oppositely Charged Nanoparticles.

Oppositely charged nanoparticles precipitate rapidly only at the point of electroneutrality, wherein their charges are macroscopically compensated. We investigated the aggregation and precipitation of oppositely charged nanoparticles at concentrations ranging from 10 to 10-3  mm (based on gold atoms) by using UV/Vis measurements. We employed solutions of equally sized (4.6 nm) gold nanoparticles, which were functionalized and stabilized with either positively or with negatively charged alkanethiols. Results showed that oppositely charged nanoparticles do not precipitate if their concentration is below a certain threshold even if the electroneutrality condition is fulfilled. This finding suggests a universal behavior of chemical systems comprising oppositely charged building blocks such as ions and charged nanoparticles.

From Master-Slave to Peer-to-Peer Coupling in Chemical Reaction Networks.

Design strategy through linking a driving pH oscillator (master system) to a pH sensitive complexation, precipitation, or protonation equilibrium (slave system) has been widely used to create and control concentration oscillations of chemical entities (e.g., monovalent cations, DNA, nanoparticles) not participating in the pH oscillatory system. No systematic investigation has been carried out on how the components of these equilibria affect the characteristics of the driving pH oscillators, and this feedback effect has been often neglected in previous studies. Here we show that pH sensitive species (hydrogen carbonate, EDTA) through a pH-dependent equilibrium could significantly affect the characteristics (time period and amplitude) of the driving pH oscillators. By varying the concentration of those species we are able to control the strength of the chemical feedback from slave system to master system thus introducing a transition from master-slave coupling to peer-to-peer coupling in linked chemical systems. To illustrate this transition and coupling strategies we investigate two coupled chemical systems, namely, the bromate-sulfite pH oscillator and carbonate-carbon dioxide equilibrium and the hydrogen peroxide-thiosulfate-copper(II) and EDTA complexation equilibrium. As a sign of the peer-to-peer coupling the characteristics of the driving oscillatory systems can be tuned by controlling the feedback strength, and the oscillations can be canceled above a critical value of this parameter.

Platinum as a HOI/I2 Redox Electrode and Its Mixed Potential in the Oscillatory Briggs-Rauscher Reaction.

Pt is a common redox electrode used to follow oscillations qualitatively in the Briggs-Rauscher (BR) and the Bray-Liebhafsky (BL) reactions from the time of their discovery. Although the potential oscillations of the electrode reflect the temporal pattern of the reaction properly, there is no general agreement as to how that potential is determined by the components of the reaction mixture. In this article, first we investigate how iodine species in different oxidation states affect the potential of a Pt electrode. It was found that I(+3) and I(+5) species do not affect the potential; only I-, I2, and HOI may have an influence. Although the latter three species are always present simultaneously as participants of the rapid iodine hydrolysis equilibrium, it was found that below and above the so-called hydrolysis limit potential (HLP, where the iodide and HOI concentrations are equal) the actual potential determining redox couple is different. Below the HLP, it is the traditional I2/I- redox couple, but above the HLP, it is the HOI/I2 redox pair that determines the potential of a Pt electrode. That change in the potential control mechanism was proven experimentally by exchange current measurements. In addition, from the potential response of the Pt electrode below and above the HLP, it was possible to calculate the equilibrium constant of the iodine hydrolysis as K°H = (4.97 ± 0.20) × 10-13 M2, in rather good agreement with earlier measurements. We also studied the perturbing effect of H2O2 on the previously mentioned potentials. The concentration of H2O2 was 0.66 M, as in the BR reaction studied here. It was found that below the HLP, the perturbing effect of H2O2 was minimal but above the HLP, H2O2 shifted the mixed potential considerably down toward the HLP. In our experiments with the BR reaction, the potential oscillations of the Pt electrode crossed the HLP, indicating that from time to time the HOI concentration exceeds that of the iodide. We can conclude that although the perturbing effect of H2O2 prevents the calculation of concentrations from Pt potentials above the HLP, [I-]/[I2]1/2 ratios can be calculated as a good approximation from Pt potentials below the HLP.

Self-assembly of like-charged nanoparticles into Voronoi diagrams.

The self-assembly of nanoscopic building blocks into higher order macroscopic patterns is one possible approach for the bottom-up fabrication of complex functional systems. Macroscopic pattern formation, in general, is determined by the reaction and diffusion of ions and molecules. In some cases macroscopic patterns emerge from diffusion and interactions existing between nanoscopic or microscopic building blocks. In systems where the distribution of the interaction-determining species is influenced by the presence of a diffusion barrier, the evolving macroscopic patterns will be determined by the spatiotemporal evolution of the building blocks. Here we show that a macroscopic pattern can be generated by the spatiotemporally controlled aggregation of like-charged carboxyl-terminated gold nanoparticles in a hydrogel, where clustering is induced by the screening effect of the sodium ions that diffuse in a hydrogel. Diffusion fronts of the sodium ions and the induced nanoparticle aggregation generate Voronoi diagrams, where the Voronoi cells consist of aggregated nanoparticles and their edges are aggregation-free and nanoparticle-free zones. We also developed a simple aggregation-diffusion model to adequately describe the evolution of the experimentally observed Voronoi patterns.

Influence of myelinated retinal nerve fibers on retinal vessel density measurement with AngioVue OCT angiography.

Myelinated retinal nerve fibers (MRNF) represent an asymptomatic developmental anomaly in which myelin sheaths extend to a group of retinal nerve fibers along their intraocular portion. The additional volume of the myelin sheaths causes displacement of the axons toward the vitreous body. We investigated the effect of localized MRNF on peripapillary vessel density measurement results using optical coherence tomography (OCT) angiography. Peripapillary angioflow density measurements (PAFD, % of the analyzed retinal area) were made with the AngioVue OCT (Optovue Inc., Fremont, USA). In both cases, the predominant position of MRNF was inferonasal to the disk. Vessel density was clearly greater in the area of the MRNF than in the surrounding retina in the optic nerve head (ONH) level, but it was lower than in the surrounding retina in the retinal nerve fiber layer (RNFL) level. In the ONH level, PAFD was higher in the MRNF area than in the spatially corresponding superonasal area (Case 1: 64.6 vs. 57.6 %; Case 2: 65.8 vs. 56.3 %). In contrast, in the RNFL level, PAFD was lower in the MRNF area than in the corresponding superonasal area (Case 1: 60.1 vs. 65.4 %; Case 2: 46.5 vs. 58.5 %). Our cases show that the effect of MRNF on OCT angiography vessel density is different in the different measurement layers. Clinicians may separate decreased vessel density caused by anterior RNFL displacement in MRNF areas from that caused by nerve fiber damage in optic neuropathies by evaluating PAFD in both the ONH and RNFL levels.

Bilayer Charge Reversal and Modification of Lipid Organization by Dendrimers as Observed by Sum-Frequency Vibrational Spectroscopy.

Polyamidoamine (PAMAM) dendrimers are hyperbranched, nanosized polymers with promising biomedical applications as nanocarriers in targeted drug delivery and gene therapy. For the development of safe dendrimer-based biomedical applications it is necessary to gain an understanding of the detailed mechanism of the interactions of both cationic and anionic dendrimers with cell membranes. To characterize dendrimer-membrane interactions we applied solid-supported lipid bilayers as biomembrane models and utilized infrared-visible sum-frequency vibrational spectroscopy to independently probe the interactions of cationic G5-NH2 and anionic G4.5-COONa dendrimers with the two leaflets of the lipid bilayers. Interaction with both dendrimers led to changes in the interfacial water structure and charge density as evidenced by the changes in the OH band intensities in the sum-frequency spectra of the bilayers. Interaction with the G5-NH2 dendrimer also led to a unique inversion of the sign of the OH-stretch amplitudes, in addition to a decrease in their absolute values. We suggest that the positively charged amino groups on the G5-NH2 dendrimer surface bind to the negatively charged bilayer, while uncompensated positive charges not involved in the binding cause a reversal of the electric field and thus an opposite orientation of the interfacial water molecules. More subtle but nonetheless significant changes were seen in the relative magnitudes of the CH amplitudes. The methyl antisymmetric to symmetric stretch amplitude ratios are altered, implying changes in the tilt angles of the phospholipid alkyl chains. The conformational order of the phospholipid alkyl chains of both leaflets is also influenced by the G5-NH2 dendrimer while G4.5-COONa has no effect on the alkyl chain conformation.

Comparison of the current and a new RTVue OCT software version for detection of ganglion cell complex changes due to cataract surgery.

The purpose was to compare the current (6.3) and a novel software version (6.12) of the RTVue-100 optical coherence tomograph (RTVue OCT) for ganglion cell complex (GCC) and retinal nerve fibre layer thickness (RNFLT) changes after phacoemulsification in healthy cataract eyes, and to investigate whether version 6.12, in which image segmentation is improved, provides benefits over version 6.3 for RNFLT and GCC imaging via mild cataract. One eye of 22 consecutive healthy cataract patients were imaged before and 1 month after uncomplicated cataract surgery using RTVue-100 OCT software version 6.3. The images were analysed with both software versions. Signal strength index increased significantly after surgery for both RNFLT and the GCC measurements (p ≤ 0.0015). No difference was seen for any RNFLT parameter between the software versions and time points (p ≥ 0.0140). The GCC values did not differ between the versions either before or after surgery (p ≥ 0.4471), but all increased significantly after surgery with software version 6.12 (p < 0.0001). Neither focal loss volume (FLV) nor global loss volume (GLV) differed between the software versions before and after surgery, respectively, but GLV decreased (improved) significantly after surgery (p = 0.010 and <0.001 for versions 6.3 and 6.12, respectively). Cataract surgery induced similar changes with both software versions, but version 6.12 identified the increase of GCC thickness and the decrease of GLV better than the current version. Although no significant difference between software versions was seen before surgery, our results suggest that version 6.12 may be more precise in measuring GCC parameters than the currently available version.

HOI versus HOIO selectivity of a molten-type AgI electrode.

UNLABELLED: AgI electrode is often applied not only to determine iodine concentration but also to follow oscillations in the weakly acidic medium of the Bray-Liebhafsky and Briggs-Rauscher reactions where it partly follows the hypoiodous acid (HOI) concentration. It is known that HOI attacks its matrix in the corrosion reaction: AgI + HOI + H(+) ⇆ Ag(+) + I2 + H2O and the AgI electrode measures the silver ion concentration produced in that reaction. The signal of the electrode can be the basis of sensitive and selective HOI concentration measurements only supposing that an analogous corrosive reaction between AgI and iodous acid (HOIO) can be neglected. To prove that assumption, the authors calibrated a molten-type AgI electrode for I(-), Ag(+), HOI, and HOIO in 1 M sulfuric acid and measured the electrode potential in the disproportionation of HOIO, which is relatively slow in that medium. Measured and simulated electrode potential versus time diagrams showed good agreement, assuming that the electrode potential is determined by the HOI concentration exclusively and the contribution of HOIO is negligible. An independent and more direct experiment was also performed giving the same result. HOIO was produced with a new improved recipe. CONCLUSION: an AgI electrode can be applied to measure the HOI concentration selectively above the so-called solubility limit potential.

[Retinal ganglion cell layer and visual function in patients with progressive external ophthalmoplegia caused by common mtDNA deletion]. / Retinalis idegrostréteg és látásfunkciók az mtDNS common deléciója által okozott progresszív ophthalmoplegia externa esetében.

AIM: Mitochondrial (mt) disorders are metabolic conditions with multiorgan involvement, which often cause neuroophtalmological symptoms. The aim of the study was to investigate the relation between progressive external ophthalmoplegia (PEO), visual pathway and mitochondrial DNA (mtDNA) mutations in patients younger than 55 years of age. METHODS: Five female patients (35 to 53 years of age) with mithochondrial disease were investigated. Automated threshold perimetry (Octopus G2 test), scanning laser polarimetry (GDx-VCC and GDx-ECC) and Fourier-domain optical coherence tomography (RTVue-100 OCT) were used in addition to detailed ophthalmological examination and evaluation of visually evoked potentials (VEP). Frequent mutations of the mtDNA were investigated in the patients' blood and muscle samples. RESULTS: PEO of various severity levels was found in all patients, using clinical tests. Genetic testing showed "common deletion" of mtDNA in all cases. For both eyes of 4 patients functional and structural ophthalmic tests had normal results. In one patient decreased visual acuity, reduced retinal nerve fiber layer thickness and prolonged L3 VEP latency time were found without optic disc damage and visual field deterioration. CONCLUSION: In 4 of our 5 patients with PEO due to common deletion of mtDNA retinal ganglion cells and visual function remained normal for a long period of life.