Sclera as a Surrogate Marker for Determining AGE-Modifications in Bruch's Membrane Using a Raman Spectroscopy-Based Index of Aging

PURPOSE. Raman spectroscopy is an effective probe of advanced glycation end products (AGEs) in Bruch's membrane. However, because it is the outermost layer of the retina, this extracellular matrix is difficult to analyze in vivo with current technology. The sclera shares many compositional characteristics with Bruch's membrane, but it is much easier to access for in vivo Raman analysis. This study investigated whether sclera could act as a surrogate tissue for Raman-based investigation of pathogenic AGEs in Bruch's membrane.

METHODS. Human sclera and Bruch's membrane were dissected from postmortem eyes (n = 67) across a wide age range (33-92 years) and were probed by Raman spectroscopy. The biochemical composition, AGEs, and their age-related trends were determined from data reduction of the Raman spectra and compared for the two tissues.

RESULTS. Raman microscopy demonstrated that Bruch's membrane and sclera are composed of a similar range of biomolecules but with distinct relative quantities, such as in the heme/collagen and the elastin/collagen ratios. Both tissues accumulated AGEs, and these correlated with chronological age (R(2) = 0.824 and R(2) = 0.717 for sclera and Bruch's membrane, respectively). The sclera accumulated AGE adducts at a lower rate than Bruch's membrane, and the models of overall age-related changes exhibited a lower rate (one-fourth that of Bruch's membrane) but a significant increase with age (P <0.05).

CONCLUSIONS. The results suggest that the sclera is a viable surrogate marker for estimating AGE accumulation in Bruch's membrane and for reliably predicting chronological age. These findings also suggest that sclera could be a useful target tissue for future patient-based, Raman spectroscopy studies. (Invest Ophthalmol Vis Sci 2011;52:1593-1598) DOI:10.1167/iovs.10-6554

Process for the preparation of water-soluble cellulose hydrolysis products.

The title process comprises admixing cellulose with an ionic liq. capable of solvating or dissolving at least some of the cellulose, the ionic liq. being a compd. comprised solely of cations and anions (e.g., 1-ethyl-3-methylimidazolium sulfate) and which exists in a liq. state at a temp. at or below 150°, and in which the anions are selected from sulfate, hydrogen sulfate and nitrate; and treating the resulting solvate or soln. with an acid in the presence of water, the acid having a pKa in water of less than 2 at 25°. [on SciFinder(R)]

Dissolution and processing of cellulose using ionic liquids, cellulose solution, and regenerating cellulose.

Cellulose is dissolved in an ionic liq. without derivatization, and is regenerated in a range of structural forms without requiring the use of harmful or volatile org. solvents. Cellulose soly. and the soln. properties can be controlled by the selection of the ionic liq. constituents, with small cations and halide or pseudohalide anions favoring soln.; dissoln. can be aided by irradn. An ionic liq., [C4mim]Cl, proved to be the best for dissolving cellulose. [on SciFinder(R)]

Regenerated cellulose matrix-encapsulated active substances and method therefor.

The process involves encapsulation or immobilization of the active solid substance in a cellulose framework by regenerating cellulose dissolved in an ionic liq. solvent in a regenerating soln. The active substance can be initially present in the ionic liq. or in the regenerating solvent either as a soln. or dispersion. The invention is applicable to mol. encapsulation and to entrapping of larger particles including enzymes, nanoparticles and macroscopic components, and to the formation of bulk materials with a wide range of morphol. forms. Thus, carbamoylmethylphosphine oxide (I) encapsulated in a cellulose matrix was realized by adding I to a 10% soln. of cellulose in 1-butyl-3-methylimidazolium chloride (ionic liq.) under vigorous stirring and then removing the ionic liq. with water. [on SciFinder(R)]

Ionic liquid reconstituted cellulose composites as solid support matrices with good transparency for biocatalytic reaction.

Disclosed are composites comprising regenerated cellulose, a first active substance, a second active substance, and a linker. Thus, microcryst. cellulose was dissolved in 1-butyl-3-methylimidazolium chloride using microwave pulse heating at 120-150°, cooled to 60° to form a super-cooled liq., 20% (based on cellulose) poly(L-lysine hydrobromide) was added therein, homogenized, cast onto a glass plate, the resulting film soaked in water for at least 24 h to leach residual from the film to give a reconstituted cellulose film, showing good transparency. [on SciFinder(R)]

Process for the preparation of water-soluble cellulose hydrolysis products.

The title process comprises admixing cellulose with an ionic liq. capable of solvating or dissolving at least some of the cellulose, the ionic liq. being a compd. comprised solely of cations and anions (e.g., 1-ethyl-3-methylimidazolium sulfate) and which exists in a liq. state at a temp. at or below 150°, the cations in the ionic liq. having the general formula R1Z(R2)(R3)R4: in which Z represents a nitrogen or phosphorus atom, R1 represents a Me or Et group, each of R2 and R3, which may be the same or different, is selected from C4-8alkyl, optionally-substituted benzyl, optionally-substituted Ph, and C5-7cycloalkyl, and R4 represents C1-8 alkyl, optionally-substituted benzyl, optionally-substituted Ph or C5-7cyclohexyl; in which the optional substituents on a benzyl or Ph ring are one, two or three substituents selected from C1-4alkyl or alkoxy groups, halogen atoms and nitro groups; and treating the resulting solvate or soln. with an acid in the presence of water, the acid having a pKa in water of less than 2 at 25°. [on SciFinder(R)]

Fluorescent PET (Photoinduced Electron Transfer) Sensors with Targeting/Anchoring Modules as Molecular Versions of Submarine Periscopes for Mapping Membrane-Bounded Protons

The two families of fluorescent PET (photoinduced electron transfer) sensors (1-9) show that the effective proton density near the surface of several micelle membranes changes over 2-3 orders of magnitude as the microlocation of the sensor (with respect to the membrane) is altered via hydrophobic tuning.

High-affinity NO3 --H+ cotransport in the fungus Neurospora:Induction and control by pH and membrane voltate

High-affinity nitrate transport was examined in intact hyphae of Neurospora crassa using electrophysiological recordings to characterize the response of the plasma membrane to NO₃ ^- challenge and to quantify transport activity. The NO₃ ^--associated membrane current was determined using a three electrode voltage clamp to bring membrane voltage under experimental control and to compensate for current dissipation along the longitudinal cell axis. Nitrate transport was evident in hyphae transferred to NO₃ ^--free, N-limited medium for 15 hr, and in hyphae grown in the absence of a nitrogen source after a single 2-min exposure to 100 μM NO₃ ^-. In the latter, induction showed a latency of 40-80 min and rose in scalar fashion with full transport activity mensurable approx. 100 min after first exposure to NO₃ ^-; it was marked by the appearance of a pronounced sensitivity of membrane voltage to extracellular NO₃ ^- additions which, after induction, resulted in reversible membrane depolarizations of (+)54-85 mV in the presence of 50 μM NO₃ ^-; and it was suppressed when NH₄ ⁺, was present during the first, inductive exposure to NO₃ ^-. Voltage clamp measurements carried out immediately before and following NO₃ ^- additions showed that the NO₃ ^--evoked depolarizations were the consequence of an inward-directed current that appeared in parallel with the depolarizations across the entire range of accessible voltages -400 to +100 mV). Measurements of NO₃ ^- uptake using NO₃ ^--selective macroelectrodes indicated a charge stoichiometry for NO₃ ^- transport of 1(+):1(NO₃ ^-) with common K(m) and J(max) values around 25 μM and 75 pmol NO₃ ^- cm^-2sec^-1, respectively, and combined measurements of pH(o) and [NO₃ ^-](o) showed a net uptake of approx. 1 H⁺ with each NO₃ ^- anion. Analysis of the NO₃ ^- current demonstrated a pronounced voltage sensitivity within the normal physiological range between -300 and -100 mV as well as interactions between the kinetic parameters of membrane voltage, pH(o) and [NO₃ ^-](o). Increasing the bathing pH from 5.5 to 8.0 reduced the current and the associated membrane depolarizations 2- to 4-fold. At a constant pH(o) of 6.1, driving the membrane voltage from -350 to -150 mV resulted in an approx. 3-fold reduction in the maximum current and a 5-fold rise in the apparent affinity for NO₃ ^-. By contrast, the same depolarization effected an approx. 20% fall in the K(m) for transport as a function in [H⁺](o). These, and additional results are consistent with a charge-coupling stoichiometry of 2(H⁺) per NO anion transported across the membrane, and implicate a carrier cycle in which NO binding is kinetically adjacent to the rate-limiting step of membrane charge transit. The data concur with previous studies demonstrating a pronounced voltage-dependence to high-affinity NO₃ ^- transport system in Arabidopsis, and underline the importance of voltage as a kinetic factor controlling NO₃ ^- transport; finally, they distinguish metabolite repression of NO₃ ^- transport induction from its sensitivity to metabolic blockade and competition with the uptake of other substrates that draw on membrane voltage as a kinetic substrate.

Cable correction of membrane currents recorded from root hairs of Arabidopsis thaliana L.

Membrane currents were recorded under voltage clamp from root hairs of Arabidopsis thaliana L. using the two-electrode method. Concurrent measurements of membrane voltage distal to the point of current injection were also carried out to assess the extent of current dissipation along the root hair axis. Estimates of the characteristic cable length, λ, showed this parameter to be a function both of membrane voltage and of substrate concentration for transport. The mean value for λ at 0 mV was 103 ± 20 μm (n=17), but ranged by as much as 6-fold in any one cell for membrane voltages from -300 to +40 mV and was affected by 0.25 to 3-fold at any one voltage on raising [K⁺]₀ from 0.1 to 10 mol m^-3. Current dissipation along the length of the cells lead to serious distortions of the current-voltage [I-V) characteristic, including consistent underestimates of membrane current as well as a general linearization of the I-V curve and a masking of conductance changes in the presence of transported substrates. In some experiments, microelectrodes were also placed in neighbouring epidermal cells to record the extent of intercellular coupling. Even with current-passing microelectrodes placed at the base of root hairs, coupling was ≤5% (voltage deflection of the epidermal cell ≤5% that recorded at the site of current injection), indicating an appreciable resistance to current passage between cells. These results demonstrate the feasibility of using root hairs as a 'single-cell model' in electrophysiological analyses of transport across the higher-plant plasma membrane; they also confirmed the need to correct for the cable properties of these cells on a cell-by-cell basis. © 1994 Oxford University Press.

Development and testing of an intermediate temperature glass sealant for use in mixed ionic and electronic conducting membrane reactors

High temperature ceramic membranes have interesting possibilities for application in areas of new and developing technologies such as hydrocarbon combustion with carbon dioxide capture and electrochemical promotion of catalysis (EPOC). However, membrane module sealing remains a significant technical challenge. In this work a borosilicate glass sealant (50SiO₂·25B₂O₃·25Na₂O, mol%) was developed to fit the requirements of sealing an air separation membrane system at intermediate temperatures (300-600 °C). The seal was assessed by testing the leak rates under a range of conditions. The parameters tested included the effect of flowrate on the leak rate, the heating and cooling rates of the reactor and the range of temperatures under which the system could operate. Tests for durability and reliability were also performed. It was found that the most favourable reactor configuration employed a reactor with the ceramic pellet placed underneath the inner chamber alumina tube (inverted configuration), using a quartz wool support to keep the membrane in place prior to sealing. Using this configuration the new glass-based seal was found to be a more suitable sealant than traditional alternatives; it produced lower leak rates at all desirable flowrates, with the potential for rapid heating and cooling and multiple cycling, allowing for prolonged usage. © 2010 Elsevier B.V. All rights reserved.

Hydrogen-permeation characteristics of a SrCeO3-based ceramic separation membrane:Thermal, ageing and surface-modification effects

Dense ceramics with mixed protonic-electronic conductivity are of considerable interest for the separation and purification of hydrogen and as electrochemical reactors. In this work, the hydrogen permeability of a Sr_0.97Ce_0.9Yb_0.1O_{3 - δ} (SCYb) membrane with a porous Pt catalytic layer on the hydrogen feed-exposed side has been studied over the temperature range 500-804 °C employing Ar as the permeate sweep gas. A SiO₂-B₂O₃-BaO-MgO-ZnO-based glass-ceramic sealant was successfully employed to seal the membrane to the dual-chamber reactor. After 14 h of exposure to 10% H₂:90% N₂ at 804 °C, the H₂ flux reached a maximum of 33 nmol cm^{- 2} s^{- 1}, over an order of magnitude higher than that obtained on membranes of similar thickness without surface modification. The permeation rate then decreased slowly and moderately on annealing at 804 °C over a further 130 h. Thereafter, the flux was both reproducible and stable on thermal cycling in the range 600-804 °C. The results indicate an important role of superficial activation processes in the flux rate and suggest that hydrogen fluxes can be further optimised in cerate-based perovskites. © 2009 Elsevier B.V. All rights reserved.

In situ catalyst activity control in a novel membrane reactor-Reaction driven wireless electrochemical promotion of catalysis

A dual chamber membrane reactor was used in order to study the effect of macroscopically applied oxygen chemical potential differences to a platinum catalyst supported on a mixed oxygen ion and electronic conducting membrane. It is believed that the oxygen chemical potential difference imposed by the use of an oxygen sweep in one of the reactor chambers causes the back-spillover of oxygen species from the support onto the catalyst surface, resulting in the modification of the catalytic activity. The use of different sweep gases, such as ethylene and hydrogen was investigated as the means to reverse the rate modification by removing the spilt over species from the catalyst surface and returning the system to its initial state. Oxygen sweep in general had a positive effect on the reaction rate with rate increases up to 20% measured. Experimental results showed that hydrogen is a more potent sweep gas than ethylene in terms of the ability to reverse rate modification. A 10% rate loss was observed when using an ethylene sweep as compared with an almost 60% rate decrease when hydrogen was used as the sweep gas. © 2009 Elsevier Ltd. All rights reserved.

Remote control of the activity of a Pt catalyst supported on a mixed ionic electronic conducting membrane

A novel configuration for the in situ control of the catalytic activity of a polycrystalline Pt catalyst supported on a mixed ionic electronic conducting (MIEC) substrate is investigated. The modification of the catalytic activity is achieved by inducing the reverse spillover of oxygen promoting species from the support onto the catalyst surface, thus modifying the chemisorptive bond energy of the gas phase adsorbed reactants. This phenomenon is known as Electrochemical Promotion of Catalysis (EPOC). In this work we investigate the use of a wireless system that takes advantage of the mixed ionic electronic conductivity of the catalyst support (internally short-circuiting the system) in a dual chamber reactor. In this wireless configuration, the reaction takes place in one chamber of the membrane reactor while introduction of the promoting species is achieved by the use of an appropriate sweep gas (and therefore control of the oxygen chemical potential difference across the membrane) on the other chamber. Experimental results have shown that the catalytic rate can be enhanced by using an oxygen sweep, while a hydrogen sweep can reverse the changes. Total rate enhancement ratios of up to 3.5 were measured. © 2008 Elsevier B.V. All rights reserved.