Small Water Channel Research Articles

Effect of Arsenate and p-Phenylenediamine on the Expression of Aquaporins in Cultured Human Urothelial Cells.

Exposure to arsenic (As) orp‑phenylenediamine (PPD) can lead to dysfunction, or even cancer, in various types of organs, including the urinary bladder, yet the underlying mechanisms remain unclear. Aquaporins (AQPs) are widely expressed small water channel proteins that provide the major route for the transport of water and other small molecules across plasma membranes in diverse cell types. Altered expression of AQPs has been associated with pathologies in all major organs, including the urinary bladder. The presentin vitrostudy was performed as a first step towards exploring the possible involvement of AQPs in As- and PPD‑induced bladder diseases. An immortalized normal human urothelial cell line was employed. Cells were exposed to different concentrations of sodium arsenate (0‑20 μM) or PPD (0‑200 μM) for 48 h. Cell viability was subsequently assessed. The mRNA and protein expression levels of AQPs (specifically, AQP3, 4, 7, 9, and 11) were analyzed using reverse transcription‑quantitative polymerase chain reaction and Western blot analyses, respectively. The viability of the cells was decreased in a concentration-dependent manner upon exposure to arsenate. The mRNA and protein expression levels of AQP3, 4, 7, and 9 were substantially reduced, whereas the expression of AQP11 was largely unchanged. As for the experiments with PPD, treatment with increasing concentrations of PPD induced a gradual decrease in cell viability. The mRNA and protein expression levels of AQP3, 4, and 11 were generally unaltered; however, a marked reduction in the expression levels of AQP7 was observed, contrasting with a gradual concentration-dependent decrease in the expression of AQP9. The importance of the differential expression profiles of the AQPs induced by arsenate and PPD requires further investigation; nevertheless, the findings of the present study suggest that AQPs have a role in As‑ and PPD‑induced bladder diseases.

THE INVESTIGATIONS OF THE NESTING STATUS OF THE GREEN TURTLE CHELONIA MYDAS ON YENIYURT BEACH (HATAY) IN THE NORTHEASTERN MEDITERRANEAN, TURKEY

A new nesting site that is not previously designated as a nesting beach was investigated for the green turtle (Chelonia mydas) nesting. The Yeniyurt Beach is bordered by BOTAŞ Port to the south and Secil Holiday Houses to the north. The small water channel in Yeniyurt Public Beach is taken to the reference point of which can be divided as the north, 2600 m long, and the south, 1400 m long. The beach was monitored between 15 June and 15 September in 2019. A total of 182 green turtle emergences occurred, and 85 (46.7%) of them were recorded as nests. The nest density was found as 21.2 clutches yr-1. The temporal distribution of the nests was found to be 52.9%, 45.8% and 1.3% in June, July and August, respectively. Besides, the average nest depth and incubation duration was 71.9cm ±8.2 (n=70) and 52.6 days ±4.4 (n=70), respectively. A total of 7362 eggs were laid in these nests and 6274 (85.2%) of them hatched. The average clutch size and number of empty eggshells were found to be 105.2 ±30.1 (40-199) and 89.6 ±26.4 (35-154), respectively. The average number of hatchlings reaching the sea was 62.8 ±20.8 (70.1%). Yeniyurt beach can be considered as a moderate dense beach (20−99 clutches yr-1; ≥6.5 clutches km-1 yr-1) for green turtle nesting based on previous studies in the Mediterranean.

Hydration and Dynamics of Full-Length Tau Amyloid Fibrils Investigated by Solid-State Nuclear Magnetic Resonance.

The microtubule-associated protein tau aggregates into distinct neurofibrillary tangles in brains afflicted with multiple neurodegenerative diseases such as Alzheimer's disease and corticobasal degeneration (CBD). The mechanism of tau misfolding and aggregation is poorly understood. Determining the structure, dynamics, and water accessibility of tau filaments may provide insight into the pathway of tau misfolding. Here, we investigate the hydration and dynamics of the β-sheet core of heparin-fibrillized 0N4R tau using solid-state nuclear magnetic resonance spectroscopy. This β-sheet core consists of the second and third microtubule-binding repeats, R2 and R3, respectively, which form a hairpin. Water-edited two-dimensional (2D) 13C-13C and 15N-13C correlation spectra show that most residues in R2 and R3 domains have low water accessibility, indicating that this hairpin is surrounded by other proteinaceous segments. However, a small number of residues, especially S285 and S316, are well hydrated compared to other Ser and Thr residues, suggesting that there is a small water channel in the middle of the hairpin. To probe whether water accessibility correlates with protein dynamics, we measured the backbone N-H dipolar couplings of the β-sheet core. Interestingly, residues in the fourth microtubule-binding repeat, R4, show rigid-limit N-H dipolar couplings, even though this domain exhibits weaker intensities in the 2D 15N-13C correlation spectra. These results suggest that the R4 domain participates in cross-β hydrogen bonding in some of the subunits but exhibits dynamic disorder in other subunits. Taken together, these hydration and dynamics data indicate that the R2-R3 hairpin of 0N4R tau is shielded from water by other proteinaceous segments on the exterior but contains a small water pore in the interior. This structural topology has various similarities with the CBD tau fibril structure but also shows specific differences. The disorder of the R4 domain and the presence of a small water channel in the heparin-fibrillized 4R tau have implications for the structure of tau fibrils in diseased brains.

Small water channel network for designing wave fields in shallow water

A small water channel network is proposed for designing shallow water fields, and the network is applied to attain water wave cloaking. The design formula is derived from an analogy between waves in a water channel and in an electric circuit; an approach of a transmission line metamaterial is extended to water waves and the water channel is used as an alternative of the transmission line. The size of the water channel is sufficiently smaller than the wavelength and a number of the channels are periodically connected as a network. This small water channel network makes artificial wave fields, and it works for a wide band of frequencies. First, we make an isotropic network equivalent to a shallow water space with constant depth in order to validate the proposed design method. It shows no wave reflection at the interface due to impedance matching. After that, the proposed theory is applied to designing an anisotropic small water channel network for demonstrating shallow water cloaking. A cylinder is cloaked from waves by the network surrounding the cylinder. Both cases are confirmed with numerical computations by solving the boundary-value problem based on linear potential theory.

Swelling of Bicontinuous Cubic Phases in Guerbet Glycolipid: Effects of Additives.

Inverse bicontinuous cubic phases of lyotropic liquid crystal self-assembly have received much attention in biomedical, biosensing, and nanotechnology applications. An Ia3d bicontinuous cubic based on the gyroid G-surface can be formed by the Guerbet synthetic glucolipid 2-hexyl-decyl-β-d-glucopyranoside (β-Glc-OC6C10) in excess water. The small water channel diameter of this cubic phase could provide nanoscale constraints in encapsulation of large molecules and crystallization of membrane proteins, hence stresses the importance of water channel tuning ability. This work investigates the swelling behavior of lyotropic self-assembly of β-Glc-OC6C10 which could be controlled and modulated by different surfactants as a hydration-modulating agent. Our results demonstrate that addition of nonionic glycolipid octyl-β-d-glucopyranoside (β-Glc-OC8) at 20 and 25 mol % gives the largest attainable cubic water channel diameter of ca. 62 Å, and formation of coacervates which may be attributed to a sponge phase were seen at 20 mol % octyl-β-d-maltopyranoside (β-Mal-OC8). Swelling of the cubic water channel can also be attained in charged surfactant-doped systems dioctyl sodium sulfosuccinate (AOT) and hexadecyltrimethylammonium bromide (CTAB), of which phase transition occurred from cubic to a lamellar phase. Destabilization of the cubic phase to an inverse hexagonal phase was observed when a high amount of charged lecithin (LEC) and stearylamine (SA) was added to the lipid self-assembly.

Stress alters the expression of aquaporins in cultured rat intestinal epithelial cells.

Aquaporins (AQPs) are widely-expressed small water channel proteins that provide the major route for water transport across plasma membranes in various cell types. Although the quantity of water transported in the intestinal tract is second only to that in the kidney, the precise role of AQPs in this organ remains largely uncertain. The present study reports the effects of hypertonic stress and ischemia/reperfusion injury on the expression of AQPs in intestinal epithelial cells. Cultured rat intestinal epithelial cells were incubated in 300 mM mannitol-containing, hypertonic culture medium or subjected to simulated ischemia/reperfusion treatment. The cell viability was evaluated by MTT assay, and the expression of AQPs was determined by semi-quantitative reverse transcription polymerase chain reaction and western blotting. Despite reduced viability, the cells exposed to hypertonic stress for 16 h demonstrated enhanced expression of AQP1 mRNA and protein. AQP9 and glycosylated AQP11 proteins were also markedly upregulated. Ischemia alone did not affect the cell viability, but subsequent reperfusion significantly reduced viability. The mRNA expression levels of all the tested AQPs were not altered by ischemia alone or by ischemia/reperfusion; however, AQP8 protein was markedly reduced by ischemic injury. In addition, treatment with ischemia alone eradicated the normally-expressed, non-glycosylated AQP11 protein whilst inducing pronounced expression of the glycosylated form. These observations may indicate that AQPs function in the intestinal epithelia in response to stress.

Deciphering a mechanism of membrane permeabilization by α-hordothionin peptide

α-Hordothionin (αHTH) belongs to thionins, the plant antimicrobial peptides with membrane-permeabilizing activity which is associated with broad-range antimicrobial activity. Experimental data have revealed a phospholipid-binding site and indicated formation of ion channels as well as membrane disruption activity of thionin. However, the mechanism of membrane permeabilization by thionin remained unknown. Here it is shown that thionin is a small water-selective channel. Unbiased high-precision molecular modeling revealed formation of a water-selective pore running through the αHTH double α-helix core when the peptide interacted with anions. Anion-induced unfolding of the C-end of the α2-helix opened a pore mouth. The pore started at the α2 C-end between the hydrophilic and the hydrophobic regions of the peptide surface and ended in the middle of the unique hydrophobic region at the C-end of the α1-helix. Highly conserved residues including cysteines and tyrosine lined the pore walls. A large positive electrostatic potential accumulated inside the pore. The narrow pore was, nonetheless, sufficient to accommodate at least one water molecule along the channel except for two constriction sites. Both constriction sites were formed by residues participating in the phospholipid-binding site. The channel properties resembled that of aquaporins with two selectivity filters, one at the entrance, inside the α2 C-end cavity, and a second in the middle of the channel. It is proposed that the αHTH water channel delivers water molecules to the bilayer center that leads to local membrane disruption. The proposed mechanism of membrane permeabilization by thionins explains seemingly controversial experimental data.

Out of the Ice

![Figure][1] CREDIT: CASEY A. CASS/UNIVERSITY OF COLORADO Three years ago, Craig Lee spied what looked like a tree branch in a small water channel streaming from a melting ice patch high in the Rocky Mountains near Yellowstone National Park. Walking over for a better look, Lee, an

Spatial Phase-Shifting Digital Holography for Three-Dimensional Particle Tracking Velocimetry

This paper presents a holographic technique for three-dimensional particle tracking. The complex amplitude on an image sensor is measured with two pairs of spatially phase-shifted digital holograms captured in a short time interval using a phase-shifting technique. Pairs of digital holograms are used to track small tracer particles in three-dimensional space and the phase-adjusted complex amplitude is employed in numerical image reconstruction to accurately detect the particles. The performance of the method is evaluated by numerical simulation. In order to demonstrate the feasibility of the method for real flow measurement, it is applied to the velocity measurement of tracer particles in a small water channel along which a high voltage is applied. The resulting components of the velocity vector in three-dimensional space are compared to those obtained using a conventional single-shot phase-shifting technique.

On the eddy system in the wake of flat circular plates in three dimensional flow

The method of colour bands for revealing the characteristics of the motion of water was first used by Osborne Reynolds some 50 years ago in the determination of the critical velocity at which the streamline motion in parallel pipes broke down. Since that time several attempts have been made to uses the same method for the study of vortex motion, but owing apparently to lack of sufficient precautions to ensure that all internal motions in the reservoir supplying the stream had disappeared before the experiments were made, the success achieved has not been as great as might have been expected. In 1910 a small water channel consisting of a rectangular canal 3 inches wide and 4 inches deep by 10 feet in length was constructed at the National Physical Laboratory for the study of the flow round plates and models and the results of a series of experiments made in the channel were described by Mr. C. G. Eden in his paper communicated to the Advisory Committee for Aeronautics. The Flow in this channel, however, was not altogether satisfactory for although the initial disturbances in the water supply were reduced by means of baffle plates and the use of a large supply tank, so that no eddies were present, there wee indications that the direction of motion at nay point was not independent of the time. The information obtained by Mr. Eden with this channel was of considerable value in revealing the nature of the flow in the wake of inclined plates and streamlined models.

Experimental Research in Aëronautics 1

Experiments on Airship Models.—During the past year further experiments have been made on the re sistance of airship models, and on the forces and moments acting on inclined models of different forms. The resistance measurements included some tests of special shapes, made at the request of the super intendent of the Royal Aircraft Factory; and an in vestigation to determine the effect of bluntness of tail on the relative air flow and on the resistance. From visual observations and photographs of the flow past models in the small water channel, made with the aid of coloured streams, it was noted that the flow in the tail region even of an elongated model was very slow. It was inferred that truncation or modification of the tail within this “dead” region should have little effect on the head resistance. A model was accordingly made in which successive sections of the tail were removable, and it was found, as expected, that the effect of the removal of portions of the tail within the “dead” region was negligibly small. In the model tested, the full length of tail was about twice the maximum diameter, and it was found that a length of 0.8 of the diameter, from the tip, could be removed without appreciable effect on the head resistance. It follows, therefore, that within this region the tail may be rounded off or otherwise modified without loss of speed; a gain in lifting power is thereby secured, while the less pointed form pre sents advantages from the constructional point of view.