Disk Membranes Research Articles

Histomorphometric Survey of Placentas of HIV-positive Mothers in Relation to their Clinical Stage in a Teaching Hospital in Uyo, South-South Nigeria.

HIV infection in pregnancy affects the mother, her placenta, and fetus resulting in perinatal/maternal morbidity and mortality. Studies show that HIV-positive mothers have several placental morphological changes. This study aimed to describe the histomorphometric parameters/lesions of placentas of HIV-positive mothers in Uyo, Akwa Ibom State, Nigeria. A prospective cross-sectional hospital-based analytical study was conducted at the departments of Obstetrics and Gynecology, and Histopathology, University of Uyo Teaching Hospital, Nigeria from December 2015 to May 2016. We studied 144 pregnant mothers (48 HIV-positive as the test group vs. 96 HIV-negative as controls). Their placentas (fetal membrane, umbilical cord, and placental disk) were collected post-delivery and evaluated (grossly/microscopically) to determine the range of histomorphometric placental parameters/lesions. Relevant obstetric data were obtained from their case notes. The test group delivered more through cesarean section than the control group (52.1% vs. 31.3%), with mean birth weights of 2.8±0.7 and 3.1±0.6 kg (p = 0.004). The mean placental weights were 57±190.1 and 664.6±167.4 g (p = 0.003), with mean placenta-birth weight ratio of 20.1±4.8 and 20.5±4.57% (p = 0.33). The test groups placental fetal membranes, umbilical cords, and disks mainly displayed acute chorioamnionitis (47.9%), acute umbilical phlebitis (14.6%), and villous vasculopathy (33.3%). The test group had a higher stage/grade of placental inflammation than the control group. In the test group, two stage 4 HIV disease state cases presented with the most severe form of placental inflammatory lesions. The commonest placental histomorphometric parameters/lesions were acute chorioamnionitis, acute umbilical phlebitis, and acute intervillositis. There was no significant association between HIV/AIDS disease stage with the most severe forms of placental inflammatory lesions.

Ceramic-like membranes without sintering via alkali activation of metakaolin, blast furnace slag, or their mixture: Characterization and cation-exchange properties

Alkali-activated (or geopolymer) membranes have emerged recently as an alternative for conventional ceramic membranes. Their main benefit is the simple and low-energy manufacturing not requiring sintering, and thus potential for clearly lower costs, while having largely similar performance as conventional ceramic materials. In this work, metakaolin, blast furnace slag, and their mixture (representing typical low, high, and medium Ca-content raw materials, respectively) were compared as aluminosilicate precursors for the preparation of self-supporting membrane disks (diameter 75 mm, height 3 mm). A thorough material characterization was performed to evaluate mechanical strength, shrinkage, microstructure, chemical composition, pore size distribution, specific surface area, zeta potential, and water flux at different temperatures (20–60 °C) and pressures (200–1000 kPa). Based on this screening, metakaolin-based membrane (i.e., the low-calcium system) indicated overall better performance than the two others based on blast furnace slag or their mixture. As a final part of the study, ammonium-containing model effluent ([NH4+] = 50 mg L−1) was distributed through the membrane (using 200 kPa pressure at 25 °C) to evaluate the potential for nitrogen removal and recovery. The mass balance examination indicated that ammonium was retained in the membrane matrix (i.e., not concentrated in the retentate fraction), and thus the likely removal mechanism was via ion-exchange. The obtained results provide interesting insights for the further development of alkali-activated membranes for applications requiring ammonium nitrogen removal, such as membrane bioreactors in municipal wastewater treatment.

Cryo-EM structures of peripherin-2 and ROM1 suggest multiple roles in photoreceptor membrane morphogenesis.

Mammalian peripherin-2 (PRPH2) and rod outer segment membrane protein 1 (ROM1) are retina-specific tetraspanins that partake in the constant renewal of stacked membrane discs of photoreceptor cells that enable vision. Here, we present single-particle cryo-electron microscopy structures of solubilized PRPH2-ROM1 heterodimers and higher-order oligomers. High-risk PRPH2 and ROM1 mutations causing blindness map to the protein-dimer interface. Cysteine bridges connect dimers forming positive-curved oligomers, whereas negative-curved oligomers were observed occasionally. Hexamers and octamers exhibit a secondary micelle that envelopes four carboxyl-terminal helices, supporting a potential role in membrane remodeling. Together, the data indicate multiple structures for PRPH2-ROM1 in creating and maintaining compartmentalization of photoreceptor cells.

Cardiac-targeted PIASy gene silencing mediates deSUMOylation of caveolin-3 and prevents ischemia/reperfusion-induced Nav1.5 downregulation and ventricular arrhythmias

BackgroundAbnormal myocardial Nav1.5 expression and function cause lethal ventricular arrhythmias during myocardial ischemia–reperfusion (I/R). Protein inhibitor of activated STAT Y (PIASy)-mediated caveolin-3 (Cav-3) SUMO modification affects Cav-3 binding to the voltage-gated sodium channel 1.5 (Nav1.5). PIASy activity is increased after myocardial I/R, but it is unclear whether this is attributable to plasma membrane Nav1.5 downregulation and ventricular arrhythmias.MethodsUsing recombinant adeno-associated virus subtype 9 (AAV9), rat cardiac PIASy was silenced using intraventricular injection of PIASy short hairpin RNA (shRNA). After two weeks, rat hearts were subjected to I/R and electrocardiography was performed to assess malignant arrhythmias. Tissues from peri-infarct areas of the left ventricle were collected for molecular biological measurements.ResultsPIASy was upregulated by I/R (P < 0.01), with increased SUMO2/3 modification of Cav-3 and reduced membrane Nav1.5 density (P < 0.01). AAV9-PIASy shRNA intraventricular injection into the rat heart downregulated PIASy after I/R, at both mRNA and protein levels (P < 0.05 vs. Scramble-shRNA + I/R group), decreased SUMO-modified Cav-3 levels, enhanced Cav-3 binding to Nav1.5, and prevented I/R-induced decrease of Nav1.5 and Cav-3 co-localization in the intercalated disc and lateral membrane. PIASy silencing in rat hearts reduced I/R-induced fatal arrhythmias, which was reflected by a modest decrease in the duration of ventricular fibrillation (VF; P < 0.05 vs. Scramble-shRNA + I/R group) and a significantly reduced arrhythmia score (P < 0.01 vs. Scramble-shRNA + I/R group). The anti-arrhythmic effects of PIASy silencing were also evidenced by decreased episodes of ventricular tachycardia (VT), sustained VT and VF, especially at the time 5–10 min after ischemia (P < 0.05 vs. Scramble-shRNA + IR group). Using in vitro human embryonic kidney 293 T (HEK293T) cells and isolated adult rat cardiomyocyte models exposed to hypoxia/reoxygenation (H/R), we confirmed that increased PIASy promoted Cav-3 modification by SUMO2/3 and Nav1.5/Cav-3 dissociation after H/R. Mutation of SUMO consensus lysine sites in Cav-3 (K38R or K144R) altered the membrane expression levels of Nav1.5 and Cav-3 before and after H/R in HEK293T cells.ConclusionsI/R-induced cardiac PIASy activation increased Cav-3 SUMOylation by SUMO2/3 and dysregulated Nav1.5-related ventricular arrhythmias. Cardiac-targeted PIASy silencing mediated Cav-3 deSUMOylation and partially prevented I/R-induced Nav1.5 downregulation in the plasma membrane of cardiomyocytes, and subsequent ventricular arrhythmias in rats. PIASy was identified as a potential therapeutic target for life-threatening arrhythmias in patients with ischemic heart diseases.

Study of Pt Alloy Catalysts for Oxygen Reduction Reaction on Rde and in MEA for High-Temperature Pemfcs

High-temperature polymer electrolyte fuel cells (HT-PEMFCs) have advantages in enhanced fuel impurities tolerance, easier heat rejection, and simpler water management[1]. Low-temperature PEMFCs with perfluorosulfonic acid electrolytes (e.g., Nafion) could not provide sufficient proton conductivity in the absence of water when T > 120 °C, limiting the application when a higher temperature is desired. High-temperature (HT-) PEMFCs have been developed by using phosphoric acid (H3PO4)-doped polymer electrolyte (e.g., polybenzimidazole, quaternary ammonium biphosphate ion pair coordinated polyphenylene, etc.) [2-4], where H3PO4 can conduct proton at high temperature up to 200 °C. Such change of the reaction environment, however, also affects oxygen reduction reaction (ORR) kinetics. Despite of a facilitated reaction kinetics under high temperature, a high Pt loading is still demanded in state-of-the-art HT-PEMFCs. To enhance ORR activity and increase Pt utilization, here we employ a strategy to alloy Pt with another transition metal (M), which has been demonstrated to be effective in LT-PEMFCs. In this study, Pt and Pt-M catalysts were used to investigate the alloy effect on the adsorption strength of H3PO4 and ORR in both half-cell rotating disk electrode (RDE) and membrane electrode assembly (MEA). In RDE study, the competition adsorption of phosphoric acid has led to a suppression on ORR activity on all catalysts, with less impact on ORR at 160 °C using pure H3PO4 than RT using 1 M H3PO4. Since alloying not just affects the O binding energy, but also H3PO4 adsorption, a different trend of ORR on Pt-M alloy catalysts was resulted in the presence of H3PO4. The alloy effect was further studied in MEA at 160 °C, which also indicates the effectiveness of using HT-RDE setup for HT-ORR catalyst screening. Reference: [1] Gittleman, C. S.; Jia, H.; De Castro, E. S.; Chisholm, C. R. I.; Kim, Y. S. Proton Conductors for Heavy-Duty Vehicle Fuel Cells. Joule 2021, 5 (7), 1660–1677.[2] Pingitore, A. T.; Huang, F.; Qian, G.; Benicewicz, B. C. Durable High Polymer Content m/ p-Polybenzimidazole Membranes for Extended Lifetime Electrochemical Devices. ACS Appl. Energy Mater. 2019, 2 (3), 1720–1726.[3] Lee, K. S.; Spendelow, J. S.; Choe, Y. K.; Fujimoto, C.; Kim, Y. S. An Operationally Flexible Fuel Cell Based on Quaternary Ammonium-Biphosphate Ion Pairs. Nat. Energy 2016, 1 (9).[4] Lim, K. H.; Lee, A. S.; Atanasov, V.; Kerres, J.; Park, E. J.; Adhikari, S.; Maurya, S.; Manriquez, L. D.; Jung, J.; Fujimoto, C.; Matanovic, I.; Jankovic, J.; Hu, Z.; Jia, H.; Kim, Y. S. Protonated Phosphonic Acid Electrodes for High Power Heavy-Duty Vehicle Fuel Cells. Nat. Energy 2022, 7 (3), 248–259.

Stir membrane liquid-phase microextraction based on milk fats hydrolysis and deep eutectic solvent formation: Determination of bisphenols

In this paper, a stir membrane liquid-phase microextraction approach based on milk fats hydrolysis and in situ deep eutectic solvent formation was developed for the first time. The approach was applied to clean-up and preconcentrate bisphenols from milk samples. The procedure assumed alkaline hydrolysis of samples fats to obtain water-soluble salts of fatty acids that acted as precursors for the deep eutectic solvent formation. A stir membrane disk impregnated with menthol was placed into the sample solution. The formation of microdroplets of the hydrophobic fatty acids was observed under sample acidification. Collection of the extract phase on the disk was based on deep eutectic solvent formation. Under optimal conditions, the RSD was < 6 %, limits of detection for bisphenols were 0.3–0.5 μg kg−1. The extraction recoveries were in the range of 95–97 %, which indicated the excellent capability of the developed approach to extract hydrophobic analytes from complex matrices.

Computational fluid dynamic simulation for hydrodynamic shear enhanced filtration in multiple shaft disk filtration system

Multiple shaft disk (MSD) filtration system, in which 12 ceramic membrane disks were inserted for creating multiple hydrodynamic shear enhanced filtration, is a promising dynamic filtration technology for water purification. In order to reveal the complex flow pattern and hydrodynamics in the internals as well as key influencing factors, the commercial CFD package FLUENT with the finite-volume method was applied to simulate the fluid flow and calculate the shear stress. Via CFD simulations, the quantitative and qualitative properties of fluid dynamics could be obtained, which was benefited to understand the multiple flow field and hydrodynamic shear performance. The higher rotating speed of ceramic membrane disk clearly improved the velocity magnitude, shear stress and turbulence, thus significantly enhancing the filtration performance. A modified mathematical model was proposed to compute the velocity entrainment factor k, which could be used to evaluate the influence of the ceramic membrane disk on fluid. The rightmost region of MSD possessed the most intense velocity magnitude, shear stress and static pressure, thus the corresponding ceramic membrane disks (disks 6 and 11) own the highest permeate flux and biggest self-cleaning ability for membrane fouling. As for the inlet flow rate, it had limited effect on the shear stress. Besides, the energy consumption and mechanical efficiency rose with the rotating speed. The pressure values in experiments were in good agreement with those of CFD simulations. The understanding of the hydrodynamic shear enhanced filtration in MSD based on CFD analysis can facilitate the design of dynamic filtration membrane system to improve the module performance and promote the water purification and fouling control.

Experimental probing of the effect of PFSA ionomer poisoning at different Pt loadings in a PEMFC

The charge-transfer resistance (Rct) in electrochemical impedance spectroscopy (EIS) was applied as an activity indicator to study the suppression of rotating disk electrodes (RDEs) and membrane electrode assemblies (MEAs) with different Pt loadings by Nafion. The use of Rct avoids the uncertainty in activity characterization caused by mass transfer in highly loaded catalyst agglomerates. Nafion exhibited a stronger poisoning effect at lower Pt loadings in both the RDEs and MEAs. The simultaneous reduction in working voltage further aggravates this poisoning, especially under low-Pt conditions. After poisoning, the normalized Rct at 20 µg/cm2 increased by 8 times at 0.9 V and 21 times at 0.82 V. When the Nafion adsorption coverage on the surface of Pt remained constant, the suppression of activity was enhanced as the Pt loading decreased. Therefore, it is critical to consider Nafion poisoning when constructing MEAs with low platinum loading and to take appropriate strategies to alleviate poisoning and achieve high-performance.

Human cone elongation responses can be explained by photoactivated cone opsin and membrane swelling and osmotic response to phosphate produced by RGS9-catalyzed GTPase

Human cone outer segment (COS) length changes in response to stimuli bleaching up to 99% of L- and M-cone opsins were measured with high resolution, phase-resolved optical coherence tomography (OCT). Responses comprised a fast phase (∼5 ms), during which COSs shrink, and two slower phases (1.5 s), during which COSs elongate. The slower components saturated in amplitude (∼425 nm) and initial rate (∼3 nm ms-1) and are well described over the 200-fold bleaching range as the sum of two exponentially rising functions with time constants of 80 to 90 ms (component 1) and 1,000 to 1,250 ms (component 2). Measurements with adaptive optics reflection densitometry revealed component 2 to be linearly related to cone pigment bleaching, and the hypothesis is proposed that it arises from cone opsin and disk membrane swelling triggered by isomerization and rate-limited by chromophore hydrolysis and its reduction to membrane-localized all-trans retinol. The light sensitivity and kinetics of component 1 suggested that the underlying mechanism is an osmotic response to an amplified soluble by-product of phototransduction. The hypotheses that component 1 corresponds to G-protein subunits dissociating from the membrane, metabolites of cyclic guanosine monophosphate (cGMP) hydrolysis, or by-products of activated guanylate cyclase are rejected, while the hypothesis that it corresponds to phosphate produced by regulator of G-protein signaling 9 (RGS9)-catalyzed hydrolysis of guanosine triphosphate (GTP) in G protein-phosphodiesterase complexes was found to be consistent with the results. These results provide a basis for the assessment with optoretinography of phototransduction in individual cone photoreceptors in health and during disease progression and therapeutic interventions.

R17C Mutation in Photoreceptor Disc-Specific Protein, PRCD, Results in Additional Lipidation Altering Protein Stability and Subcellular Localization.

Progressive rod-cone degeneration (PRCD) is a photoreceptor outer segment (OS) disc-specific protein essential for maintaining OS structures while contributing to rhodopsin packaging densities and distribution in disc membranes. Previously, we showed PRCD undergoing palmitoylation at the sole cysteine (Cys2), where a mutation linked with retinitis pigmentosa (RP) in humans and dogs demonstrates the importance of palmitoylation for protein stability and trafficking to the OS. We demonstrate a mutation, in the polybasic region (PBR) of PRCD (Arg17Cys) linked with RP where an additional lipidation is observed through acyl-RAC. Immunolocalization of transiently expressed R17C in hRPE1 cells depicts similar characteristics to wild-type PRCD; however, a double mutant lacking endogenous palmitoylation at Cys2Tyr with Arg17Cys is comparable to the C2Y protein as both aggregate, mislocalized to the subcellular compartments within the cytoplasm. Subretinal injection of PRCD mutant constructs followed by electroporation in murine retina exhibit mislocalization in the inner segment. Despite being additionally lipidated and demonstrating strong membrane association, the mutation in the PBR affects protein stability and localization to the OS. Acylation within the PBR alone neither compensates for protein stability nor trafficking, revealing defects in the PBR likely lead to dysregulation of PRCD protein associated with blinding diseases.

Optimization of an Antibody Microarray Printing Process Using a Designed Experiment.

Antibody microarrays have proven useful in immunoassay-based point-of-care diagnostics for infectious diseases. Noncontact piezoelectric inkjet printing has advantages to print antibody microarrays on nitrocellulose substrates for this application due to its compatibility with sensitive solutions and substrates, simple droplet control, and potential for high-capacity printing. However, there remain real-world challenges in printing such microarrays, which motivated this study. The effects of three concentrations of capture antibody (cAb) reagents and nozzle hydrostatic pressures were chosen to investigate three responses: the number of printed membrane disks, dispensing performance, and microarray quality. Printing conditions were found to be most ideal with 5 mg/mL cAb and a nozzle hydrostatic pressure near zero, which produced 130 membrane disks in a single print versus the 10 membrane disks per print before optimization. These results serve to inform efficient printing of antibody microarrays on nitrocellulose membranes for rapid immunoassay-based detection of infectious diseases and beyond.

Autophagy in Human Retinal Neurons in Glaucoma.

Immunohistochemical and ultrastructural analysis revealed signs of structural alterations in neurons and autophagy in all layers of the human retina at the end-stage glaucoma. The most pronounced destructive changes associated with swelling and destruction of mitochondria, endoplasmic reticulum, and Golgi apparatus, as well as structural signs of impaired synaptic activity and apoptosis were noted in ganglion, bipolar, and amacrine neurons. In the structure of photoreceptor cells, alone with destructive processes associated with structural alterations of rods and cones in the outer membrane discs, as well as swelling of organelles, we observed processes aimed at the maintenance of cell homeostasis. Structural signs of autophagy (mainly mitophagy) and changes of the ultrastructural organization in rod neurons were more pronounced than in cones.

Model-Based Performance Analysis of Membrane Reactor with Ethanol Steam Reforming over a Monolith.

Membrane reactors (MR) with an appropriate catalyst are considered to be an innovative and intensified technology for converting a fuel into the hydrogen-rich gas with the simultaneous recovery of high-quality hydrogen. Characteristics of an asymmetric membrane disk module consisting of a gas-tight nanocomposite functional coating (Ni + Cu/Nd5.5WO11.25-δ mixed proton-electron conducting nanocomposite) deposited on a gas-permeable functionally graded substrate has previously been extensively studied at lab-scale using MRs, containing the catalyst in a packed bed and in the form of a monolith. The catalytic monolith consisted of a FeCrAl substrate with a washcoat and an Ni + Ru/Pr0.35Ce0.35Zr0.35O2 active component. It has been shown that the driving potential for hydrogen permeation across the same membrane in a monolithic catalyst –assisted MR is greater compared to the packed bed catalyst. This paper presents results of the study where a one-dimensional isothermal model was used to interrelate catalytic and permeation phenomena in a MR with ethanol steam reforming over the monolith, operating at atmospheric pressure and in the temperature range of 700–900 °C. The developed mathematical reaction–transport model for the constituent layers of the catalyst-asymmetric membrane assembly together with a Sieverts’ equation for the functional dense layer, taking also into account the effect of boundary layers, was implemented in a COMSOL Multiphysics environment. Good agreement with the experimental data of the lab-scale MR with reasonable parameters values is provided. In numerical experiments, concentration profiles along the reactor axis were obtained, showing the effect of the emerging concentration gradient in the boundary layer adjacent to the membrane. Studies have shown that a MR with a catalytic monolith along with appropriate organization of a stagnant feed flow between the monolith and the membrane surface may enhance production and flux of hydrogen, as well as the efficiency characteristics of the reactor compared to a reactor with packed beds.

(Invited) Impact of Pore Morphology and Surface Hydrophobicity of the Carbon Matrix on the Macrokinetics of the Oxygen Reduction Reaction Performance for Atomically Dispersed Fe-N-C Catalysts

Atomically dispersed transition metal catalysts are an important family of non-precious metal electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. The iron-nitrogen-carbon (Fe-N-C) catalyst, wherein the iron metal centers are coordinated by nitrogen atoms (FeNx) on carbonaceous supports, exhibits outstanding ORR activity in both rotating disk electrode (RDE) and membrane electrode assembly (MEA) configurations.[1] The pore structure[2] and surface hydrophobicity[3] of the carbon matrix are of particular significance to the MEA performance, where the high current throughput requires good mass transport capability and controlled water flooding on the electrodes. In this work, we employed two widely used Fe-N-C catalysts – one pyrolyzed from metal organic framework (MOF-derived)[4] and the other produced by using the sacrificial support method (sacrificial templated)[1]. Specifically, nitrogen physisorption and water vapor physisorption were used to study the pore morphology and the specific surface hydrophobicity, respectively. As shown in Figure 1, the sacrificial templated Fe-N-C catalyst showed a significant mesoporosity as compared to the MOF-derived counterpart, while its surface was much more hydrophobic, as indicated by the less water uptake through whole pressure range (Figure 1f). Such difference of carbon morphology was further correlated to their macrokinetic performance in a MEA configuration, to reveal the impact of the morphological and hydrophilic/hydrophobic balance on these two types of Fe-N-C catalysts. Reference [1] T. Asset and P. Atanassov, Joule, 2020, 4, 33.[2] Y. Huang, Y. Chen, M. Xu, T. Asset, P. Tieu, A. Gili, D. Kulkarni, V. de Andrade, F. de Carlo, H. S. Barnard, A. Doran, D. Y. Parkinson, X. Pan, P. Atanassov, and I. Zenyuk, Materials Today, 2021, 47, 53.[3] L. Liu, S. J. Tan, T. Horikawa, D. D. Do, D. Nicholson and J. Liu, Adv Colloid Interface Sci, 2017, 250, 64.[4] K. Kumar, T. Asset, X. Li, Y. Liu, X. Yan, Y. Chen, M. Mermoux, X. Pan, P. Atanassov, F. Maillard and L. Dubau, ACS Catalysis, 11, 484. Figure 1. XRD (a) and AC-STEM (b-d) images of the Fe-N-C catalyst produced by the sacrificial support method. Nitrogen (e) and water vapor (f) physisorption isotherms of MOF-derived and sacrificial templated Fe-N-C catalysts. (g) Pore size distribution of the two catalysts by the BJH method based on the N2 adsorption branch. Figure 1

Structure and function of ABCA4 and its role in the visual cycle and Stargardt macular degeneration.

ABCA4 is a member of the superfamily of ATP-binding cassette (ABC) transporters that is preferentially localized along the rim region of rod and cone photoreceptor outer segment disc membranes. It uses the energy from ATP binding and hydrolysis to transport N-retinylidene-phosphatidylethanolamine (N-Ret-PE), the Schiff base adduct of retinal and phosphatidylethanolamine, from the lumen to the cytoplasmic leaflet of disc membranes. This ensures that all-trans-retinal and excess 11-cis-retinal are efficiently cleared from photoreceptor cells thereby preventing the accumulation of toxic retinoid compounds. Loss-of-function mutations in the gene encoding ABCA4 cause autosomal recessive Stargardt macular degeneration, also known as Stargardt disease (STGD1), and related autosomal recessive retinopathies characterized by impaired central vision and an accumulation of lipofuscin and bis-retinoid compounds. High resolution structures of ABCA4 in its substrate and nucleotide free state and containing bound N-Ret-PE or ATP have been determined by cryo-electron microscopy providing insight into the molecular architecture of ABCA4 and mechanisms underlying substrate recognition and conformational changes induced by ATP binding. The expression and functional characterization of a large number of disease-causing missense ABCA4 variants have been determined. These studies have shed light into the molecular mechanisms underlying Stargardt disease and a classification that reliably predicts the effect of a specific missense mutation on the severity of the disease. They also provide a framework for developing rational therapeutic treatments for ABCA4-associated diseases.

The Green Placental Disk: Massive Placental Disk Bilirubin Deposition Due to Maternal Hyperbilirubinemia

Background Bile staining in the hepatobiliary tree is a well-known phenomenon, but bilirubin can also be deposited in and stain the umbilical cord, amniotic fluid, placental disk and placental membranes. Case Report We present a placenta with grossly greenish discoloration of the placental disk and microscopic villous bilirubin deposition due to maternal hyperbilirubinemia. Conclusion: Maternal hyperbilirubinemia causes massive bilirubin deposition in villous synctiotrophoblasts and Hofbauer cells leading to grossly green discoloration of the placental disk.

Targeting the HDAC6-Cilium Axis Ameliorates the Pathological Changes Associated with Retinopathy of Prematurity.

Retinopathy of prematurity (ROP) is one of the leading causes of childhood visual impairment and blindness. However, there are still very few effective pharmacological interventions for ROP. Histone deacetylase 6 (HDAC6)‐mediated disassembly of photoreceptor cilia has recently been implicated as an early event in the pathogenesis of ROP. Herein it is shown that enhanced expression of HDAC6 by intravitreal injection of adenoviruses encoding HDAC6 induces the typical pathological changes associated with ROP in mice, including disruption of the membranous disks of photoreceptor outer segments and a decrease in electroretinographic amplitudes. Hdac6 transgenic mice exhibit similar ROP‐related defects in retinal structures and functions and disassembly of photoreceptor cilia, whereas Hdac6 knockout mice are resistant to oxygen change‐induced retinal defects. It is further shown that blocking HDAC6‐mediated cilium disassembly by intravitreal injection of small‐molecule compounds protect mice from ROP‐associated retinal defects. The findings indicate that pharmacological targeting of the HDAC6‐cilium axis may represent a promising strategy for the prevention of ROP.

Structural Abnormalities of the Optic Nerve and Retina in Huntington's Disease Pre-Clinical and Clinical Settings.

Huntington’s disease (HD) is a fatal neurodegenerative disorder caused by a polyglutamine expansion in the huntingtin protein. HD-related pathological remodelling has been reported in HD mouse models and HD carriers. In this study, we studied structural abnormalities in the optic nerve by employing Spectral Domain Optical Coherence Tomography (SD-OCT) in pre-symptomatic HD carriers of Caucasian origin. Transmission Electron Microscopy (TEM) was used to investigate ultrastructural changes in the optic nerve of the well-established R6/2 mouse model at the symptomatic stage of the disease. We found that pre-symptomatic HD carriers displayed a significant reduction in the retinal nerve fibre layer (RNFL) thickness, including specific quadrants: superior, inferior and temporal, but not nasal. There were no other significant irregularities in the GCC layer, at the macula level and in the optic disc morphology. The ultrastructural analysis of the optic nerve in R6/2 mice revealed a significant thinning of the myelin sheaths, with a lamellar separation of the myelin, and a presence of myelonoid bodies. We also found a significant reduction in the thickness of myelin sheaths in peripheral nerves within the choroids area. Those ultrastructural abnormalities were also observed in HD photoreceptor cells that contained severely damaged membrane disks, with evident vacuolisation and swelling. Moreover, the outer segment of retinal layers showed a progressive disintegration. Our study explored structural changes of the optic nerve in pre- and clinical settings and opens new avenues for the potential development of biomarkers that would be of great interest in HD gene therapies.

Capabilities and limitations of rotating disk electrodes versus membrane electrode assemblies in the investigation of electrocatalysts

Capabilities and limitations of rotating disk electrodes versus membrane electrode assemblies in the investigation of electrocatalysts

Extent of Internal Hydration influence the Activation of GPCR Rhodopsin

Rhodopsin is an archetypical GPCR responsible for dim‐light vision, which adopts a dynamic equilibrium between two metastable intermediates, metarhodopsin‐I (MI) and metarhodopsin‐II (MII), upon absorption of light. MI is an inactive conformational state of this GPCR, while MII is a fully active conformational state. We hypothesized that the MI to MII transition following isomerization of the retinal ligand involves a flood of bulk water into the protein core. To observe this change in the hydration level of the receptor during activation that is typically invisible to structural techniques such as X‐ray crystallography or cryo‐EM, we carried out a set of experiments using an osmotic stress approach. In this approach, the hydration level of rhodopsin was changed by placing the protein in native disk membranes in solutions with varying levels of osmotic pressure. Inert hydrophilic polyethylene glycol (PEG) solutes with different molecular weights and concentrations were used as the osmolytes. The effect of osmotic pressure on conformational dynamics was then quantified by measuring the reversible shifting of the metarhodopsin equilibrium using UV‐Visible spectroscopy. Results from these experiments show an influx of 80–100 water molecules into the rhodopsin interior, forming a partially disordered, solvent‐swollen active MII conformational state during photoactivation, a result supported by atomistic molecular dynamics simulations work [1, 2]. Additionally, we observed that the size of the polymer osmolyte played an important role in the modulation of rhodopsin’s activation: large osmolytes (PEG &gt; 600) back shift the equilibrium to inactive MI state, while small osmolytes (PEG &lt; 600) forward‐shift the equilibrium to MII state. We attribute this size dependence to the degree of osmolyte penetration into the rhodopsin core. Large polymers behave similarly to ideal osmolytes and dehydrate rhodopsin, while smaller polymers wriggle into the rhodopsin interior and stabilize the open MII conformation. These results necessitate a new understanding of GPCR activation in which the hydration level of protein is paramount in governing conformational energy landscapes. [1] U. Chawla et al. (2021) Angew. Chem. Int. Ed. 60, 2288–2295. [2] N. Leioatts et al. (2014) Biochemistry 53, 376−385.