Changes to zonular tension alters the subcellular distribution of AQP5 in regions of influx and efflux of water in the rat lens

ABSTRACTPurposeThe lens utilizes circulating fluxes of ions and water that enter the lens at both poles and exit at the equator to maintain its optical properties. We have mapped the subcellular distribution of the lens aquaporins (AQP0, 1, & 5) in these water influx and efflux zones and investigated how their membrane location is affected by changes in tension applied to the lens by the zonules.MethodsImmunohistochemistry using AQP antibodies was performed on axial sections obtained from rat lenses that had been removed from the eye and then fixed, or were fixed in situ to maintain zonular tension. Zonular tension was pharmacologically modulated by applying either tropicamide (increased), or pilocarpine (decreased). AQP labelling was visualized using confocal microscopy.ResultsModulation of zonular tension had no effect on AQP1 or AQP0 labelling in either the water efflux, or influx zones. In contrast, AQP5 labelling changed from membranous to cytoplasmic in response to both mechanical and pharmacologically induced reductions in zonular tension in both the efflux zone, and anterior (but not posterior) influx zone associated with the lens sutures.ConclusionsAltering zonular tension dynamically regulates the membrane trafficking of AQP5 in the efflux and anterior influx zones to potentially change the magnitude of circulating water fluxes in the lens.

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Genetic and pharmacological inactivation of apical Na+-K+-2Cl− cotransporter 1 in choroid plexus epithelial cells reveals the physiological function of the cotransporter

AJP Cell Physiology ◽

10.1152/ajpcell.00026.2018 ◽

2019 ◽

Vol 316 (4) ◽

pp. C525-C544 ◽

Cited By ~ 18

Author(s):

Jeannine M. C. Gregoriades ◽

Aaron Madaris ◽

Francisco J. Alvarez ◽

Francisco J. Alvarez-Leefmans

Keyword(s):

Epithelial Cells ◽

Choroid Plexus ◽

Basolateral Membrane ◽

Water Volume ◽

Water Fluxes ◽

Membrane Location ◽

Flux Mode ◽

Choroid Plexus Epithelial

Choroid plexus epithelial cells (CPECs) secrete cerebrospinal fluid (CSF). They express Na+-K+-ATPase and Na+-K+-2Cl− cotransporter 1 (NKCC1) on their apical membrane, deviating from typical basolateral membrane location in secretory epithelia. Given this peculiarity, the direction of basal net ion fluxes mediated by NKCC1 in CPECs is controversial, and cotransporter function is unclear. Determining the direction of basal NKCC1-mediated fluxes is critical to understanding the function of apical NKCC1. If NKCC1 works in the net efflux mode, it may be directly involved in CSF secretion. Conversely, if NKCC1 works in the net influx mode, it would have an absorptive function, contributing to intracellular Cl− concentration ([Cl−]i) and cell water volume (CWV) maintenance needed for CSF secretion. We resolve this long-standing debate by electron microscopy (EM), live-cell-imaging microscopy (LCIM), and intracellular Na+ and Cl− measurements in single CPECs of NKCC1+/+ and NKCC1−/− mouse. NKCC1-mediated ion and associated water fluxes are tightly linked, thus their direction is inferred by measuring CWV changes. Genetic or pharmacological NKCC1 inactivation produces CPEC shrinkage. EM of NKCC1−/− CPECs in situ shows they are shrunken, forming large dilations of their basolateral extracellular spaces, yet remaining attached by tight junctions. Normarski LCIM shows in vitro CPECs from NKCC1−/− are ~17% smaller than NKCC1+/+. CWV measurements in calcein-loaded CPECs show that bumetanide (10 μM) produces ~16% decrease in CWV in NKCC1+/+ but not in NKCC1−/− CPECs. Our findings suggest that under basal conditions apical NKCC1 is continuously active and works in the net inward flux mode maintaining [Cl−]i and CWV needed for CSF secretion.

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Hyperspectral Remote Sensing of the Coastal Ocean: Adaptive Sampling and Forecasting of In situ Optical Properties

10.21236/ada624963 ◽

2001 ◽

Author(s):

Oscar Schofield ◽

Scott Glenn ◽

Dale Haidvogel ◽

Frederick Grassle

Keyword(s):

Remote Sensing ◽

Optical Properties ◽

Adaptive Sampling ◽

Coastal Ocean ◽

Hyperspectral Remote Sensing

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Developing the Ability to Map In situ Optical Properties in Coastal Waters using Slocum Coastal Gliders

10.21236/ada629246 ◽

2003 ◽

Author(s):

Oscar Schofield ◽

Scott Glenn ◽

Clayton Jones

Keyword(s):

Optical Properties ◽

Coastal Waters

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B0AT1 amino acid transporter complexed with SARS-CoV-2 receptor ACE2 forms a heterodimer functional unit: in situ conformation using radiation inactivation analysis

Function ◽

10.1093/function/zqab027 ◽

2021 ◽

Author(s):

Bruce R Stevens ◽

J Clive Ellory ◽

Robert L Preston

Keyword(s):

Amino Acid ◽

Membrane Trafficking ◽

Functional Unit ◽

Membrane Vesicles ◽

High Energy ◽

Amino Acid Transporter ◽

Neutral Amino Acid ◽

Transport Activity ◽

Acid Transporter

Abstract The SARS-CoV-2 receptor, Angiotensin Converting Enzyme-2 (ACE2), is expressed at levels of greatest magnitude in the small intestine as compared to all other human tissues. Enterocyte ACE2 is co-expressed as the apical membrane trafficking partner obligatory for expression and activity of the B0AT1 sodium-dependent neutral amino acid transporter. These components are assembled as an [ACE2: B0AT1]2 dimer-of-heterodimers quaternary complex that putatively steers SARS-CoV-2 tropism in the gastrointestinal (GI) tract. GI clinical symptomology is reported in about half of COVID-19 patients, and can be accompanied by gut shedding of virion particles. We hypothesized that within this 4-mer structural complex, each [ACE2: B0AT1] heterodimer pair constitutes a physiological “functional unit.” This was confirmed experimentally by employing purified lyophilized enterocyte brush border membrane vesicles that were exposed to increasing doses of high-energy electron radiation from a 16 MeV linear accelerator. Based on established target theory, the results indicated the presence of Na+-dependent neutral amino acid influx transport activity functional unit with target size mw = 183.7 ± 16.8 kDa in situ in intact apical membranes. Each thermodynamically stabilized [ACE2: B0AT1] heterodimer functional unit manifests the transport activity within the whole ∼345 kDa [ACE2: B0AT1]2 dimer-of-heterodimers quaternary structural complex. The results are consistent with our prior molecular docking modeling and gut-lung axis approaches to understanding COVID-19. These findings advance the understanding of the physiology of B0AT1 interaction with ACE2 in the gut, and thereby potentially contribute to translational developments designed to treat or mitigate COVID-19 variant outbreaks and/or GI symptom persistence in long-haul Post-Acute Sequelae of SARS-CoV-2 (PASC).

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Evaluating model parameterizations of submicron aerosol scattering and absorption with in situ data from ARCTAS 2008

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-9435-2016 ◽

2016 ◽

Vol 16 (14) ◽

pp. 9435-9455 ◽

Cited By ~ 8

Author(s):

Matthew J. Alvarado ◽

Chantelle R. Lonsdale ◽

Helen L. Macintyre ◽

Huisheng Bian ◽

Mian Chin ◽

...

Keyword(s):

Optical Properties ◽

Size Distribution ◽

Aerosol Size Distribution ◽

Visible Radiation ◽

Submicron Aerosol ◽

In Situ Data ◽

Aerosol Absorption ◽

Aerosol Scattering ◽

The Impact

Abstract. Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10–23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction throughout the aerosol size distribution. Using a core-shell mixing rule in ASP overestimates aerosol absorption, especially for the fresh biomass burning aerosol measured in ARCTAS-B, suggesting the need for modeling the time-varying mixing states of aerosols in future versions of ASP.

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