Active Ion Transport Research Articles

Proton-transporting heliorhodopsins from marine giant viruses.

Rhodopsins convert light into signals and energy in animals and microbes. Heliorhodopsins (HeRs), a recently discovered new rhodopsin family, are widely present in archaea, bacteria, unicellular eukaryotes, and giant viruses, but their function remains unknown. Here, we report that a viral HeR from Emiliania huxleyi virus 202 (V2HeR3) is a light-activated proton transporter. V2HeR3 absorbs blue-green light, and the active intermediate contains the deprotonated retinal Schiff base. Site-directed mutagenesis study revealed that E191 in TM6 constitutes the gate together with the retinal Schiff base. E205 and E215 form a PAG of the Schiff base, and mutations at these positions converted the protein into an outward proton pump. Three environmental viral HeRs from the same group as well as a more distantly related HeR exhibited similar proton-transport activity, indicating that HeR functions might be diverse similarly to type-1 microbial rhodopsins. Some strains of E. huxleyi contain one HeR that is related to the viral HeRs, while its viruses EhV-201 and EhV-202 contain two and three HeRs, respectively. Except for V2HeR3 from EhV-202, none of these proteins exhibit ion transport activity. Thus, when expressed in the E. huxleyi cell membranes, only V2HeR3 has the potential to depolarize the host cells by light, possibly to overcome the host defense mechanisms or to prevent superinfection. The neuronal activity generated by V2HeR3 suggests that it can potentially be used as an optogenetic tool, similarly to type-1 microbial rhodopsins.

A 24-epibrassinolide treatment and intercropping willow with alfalfa increase the efficiency of the phytoremediation of cadmium-contaminated soil

Cadmium contamination in agricultural soils threatens food security and human health, and that has caused widespread concern worldwide. Willow and alfalfa are widely used for the phytoremediation of cadmium (Cd)-contaminated soil, and willow NJU513 is the promising plant for remediating Cd-contaminated soil. In order to discuss the effect of intercropping willow NJU513 with alfalfa on the phytoremediation of Cd-contaminated soil, a pot-culture experiment was conducted in the greenhouse. The result showed that the phytoremediation of Cd-contaminated soil was enhanced by this intercropping because of the 25.90 % increase in the available Cd content. In order to increase the phytoremediation efficiency of Cd in the intercropping treatment, a 24-epibrassinolide (Brs) treatment was designed in the current study. The results showed that the phytoremediation of Cd-contaminated soil by willow and alfalfa improved following a Brs treatment because of the 16.32–74.15 % and 16.91–44.48 % increases in the plant biomass and available Cd content, respectively. Additionally, the extracted Cd by plants in the intercropping treatments with and without Brs was 0.56 and 0.31 mg pot−1, respectively. Transcriptome analyses of willow leaves revealed that Brs up-regulated the expression of genes related to calcium channel activity, calcium and zinc transmembrane transport, photosynthesis, catalase/antioxidant activity, glutathione metabolic processes and detoxification, phagosomes, and vacuoles, and that these upregulated genes promoted plant remediation efficiency and resistance to Cd stress. Brs promoted the phosphate ion transporter activity in willow leaves, which may have enhanced the solubilization of insoluble phosphate minerals by bacterial species (e.g., Vicinamibacterales, Bacillus, and Gaiella) to release Cd, ultimately leading to increased phytoremediation efficiency. In addition, plants with and without Brs treatments induced the bacteria-mediated transformation of available Cd to stable Cd. The study findings may be useful for improving the phytoremediation of Cd-contaminated paddy soil.

The change of the electrophysiological parameters using human intestinal tissues from ulcerative colitis and Crohn's disease

The purpose of this study was to investigate how disease state of the UC and CD patients affect tissue function determined from electrophysiology viewpoint the electrophysiological parameters on normal, ulcerative colitis (UC) and Crohn's disease (CD) patients. Potential differences (PD), short circuit current (Isc) and resistance (R) as electrophysiological parameters were determined using human large intestinal tissues.The measure of autoptical abnormality was quantified on an arbitrary scale of 0–2. A severe effect of ulcer and thickened mucosa by fibrosis was scored as Grade 2. The larger number of autopsy grade on both UC and CD tissues, the lower values of PD and R than those of normal tissues were observed, although Isc values were not statistically changed irrespective of autopsy grade. This electrophysiological observation of reduced PD indicated functional impairment of active ion transport via ion pumps. Additionally, the R values of CD tissues on each autopsy grade tended to be lower than those of UC tissues. These results suggest that the effect of inflammatory bowel disease on barrier function is different between UC and CD tissues. Therefore, the fibrosis on CD patients might affect the electrophysiological parameters than that of UC patients.

Cation-Selective Oxide Semiconductor Mesoporous Membranes for Biomimetic Ion Rectification and Light-Powered Ion Pumping.

Artificial membranes precisely imitating the biological functions of ion channels and ion pumps have attracted significant attention to explore nanofluidic energy conversion. Herein, inspired by the cyclic ion transport for the photosynthesis in purple bacteria, a bilayer inorganic membrane (TiO2 /AAO) composed of oxide semiconductor (TiO2 ) mesopores on anodic alumina (AAO) macropores is wedeveloped. This inorganic membrane achieves the functions of ion channels and ion pumps, including the ion rectification and light-powered ion pumping. The asymmetric charge distribution across the bilayer membrane contributes to the cationic selectivity and ion rectification characteristics. The electrons induced by ultraviolet irradiation introduce a built-in electric field across TiO2 /AAO membrane, which pumps the active ion transport from a low to a high concentration. This work integrates the functions of biological ion channels and ion pumps within an artificial membrane for the first time, which paves the way to explore multifunctional membranes analogous to its biological counterpart.

Biological effects of inhaled crude oil vapor. II. Pulmonary effects

Workers involved in oil exploration and production in the upstream petroleum industry are exposed to crude oil vapor (COV). COV levels in the proximity of workers during production tank gauging and opening of thief hatches can exceed regulatory standards, and several deaths have occurred after opening thief hatches. There is a paucity of information regarding the effects of COV inhalation in the lung. To address these knowledge gaps, the present hazard identification study was undertaken to investigate the effects of an acute, single inhalation exposure (6 h) or a 28 d sub-chronic exposure (6 h/d × 4 d/wk × 4 wks) to COV (300 ppm; Macondo well surrogate oil) on ventilatory and non-ventilatory functions of the lung in a rat model 1 and 28 d after acute exposure, and 1, 28 and 90 d following sub-chronic exposure. Basal airway resistance was increased 90 d post-sub-chronic exposure, but reactivity to methacholine (MCh) was unaffected. In the isolated, perfused trachea preparation the inhibitory effect of the airway epithelium on reactivity to MCh was increased at 90 d post-exposure. Efferent cholinergic nerve activity regulating airway smooth muscle was unaffected by COV exposure. Acute exposure did not affect basal airway epithelial ion transport, but 28 d after sub-chronic exposure alterations in active (Na+ and Cl¯) and passive ion transport occurred. COV treatment did not affect lung vascular permeability. The findings indicate that acute and sub-chronic COV inhalation does not appreciably affect ventilatory properties of the rat, but transient changes in airway epithelium occur.

Self-supported Co-Ni-S@CoNi-LDH electrode with a nanosheet-assembled core-shell structure for a high-performance supercapacitor

In this work, a nanosheet-assembled core-shell structure composite of Co-Ni-S@CoNi-LDH was prepared on Ni foam via hydrothermal synthesis, in which Co-Ni-S nanowires as cores were assembled with the shell of CoNi-LDH nanosheets. The combination of the high conductivity of Co-Ni-S, the high specific surface area of CoNi-LDH and the multivalent state of Ni and Co provided more active sites, short and effective ion transport paths, and great synergy, which played significant roles in the excellent performance of Co-Ni-S@CoNi-LDH. Meanwhile, the nanosheet-assembled core-shell structure improved the overall stability. Based on the characterisation and the performance measurements, the Co-Ni-S@CoNi-LDH electrode showed an excellent electrochemical performance. The Co-Ni-S@CoNi-LDH electrode acquired a specific capacitance of 2414 F/g at a 1 A/g current density and a high cycle stability with an 89.7% retention after 3000 cycles. The assembled hybrid supercapacitor Co-Ni-S@CoNi-LDH//AC delivered a high energy density of 59.11 Wh kg −1 at an 855.43 W kg −1 power density, as well as an excellent rate performance of 81% after 5000 cycles at a 5 A/g current density, showing good potential for practical applications. • Nanosheets are assembled oriented on the nanowires by hydrothermal synthesis. • The effects of the reactants ratio on the structure were investigated. • The Co-Ni-S@CoNi-LDH delivers a high gravimetric specific capacity of 2414 F/g. • Co-Ni-S@CoNi-LDH//AC device was assembled with excellent electrochemical performance.

P455: BREAKING THE PUMP: TARGETING THE SODIUM-POTASSIUM PUMP AS A THERAPEUTIC STRATEGY IN ACUTE MYELOID LEUKEMIA

Background: Acute myeloid leukemia (AML) is a heterogenous hematologic malignancy with poor overall survival despite intensive cytotoxic chemotherapy and newer targeted agents. With a 5-year survival rate of only 29% in adults with AML, new therapeutic strategies are needed. Aims: In order to identify novel, selective targets for AML, we used the Cancer Dependency Map, which provides genome-scale CRISPR/Cas9 depletion screen data in hundreds of cancer cell lines. Here, we identified ATP1B3 as a context-specific dependency that could be therapeutically exploited. ATP1B3 is the smaller glycoprotein subunit (beta) of the sodium-potassium pump (Na/K-ATP pump). Together with the catalytic alpha subunit ATP1A1, it forms a heterodimer located in the plasma membrane, regulating the electrochemical gradient through the transport of Na and K ions across the membrane. The Na/K-ATP pump is of vital importance in the maintenance of cellular homeostasis and membrane potential and because of its function as a receptor and signal transducer. While the ATP1A1 carries out ion transport and enzymatic activity, making it a common essential gene (a gene which ranks among the most depleted genes in at least 90% of screened cell lines), ATP1B3 is not essential in all cancer cells. This beta subunit seems to be crucial for intracellular transport and stabilization of the alpha subunit in the membrane. The beta subunit has 4 paralogs, showing similar expression patterns among tissues, with one exception, ATP1B1. Methods: We used a diverse panel of functional genomic based assays, validating our finding using CRISPR/Cas9 knockout and overexpression constructs for the Na/K-ATP pump beta subunit paralogs. In an approach to analyze protein-protein interactions we generated BioID constructs for a mass spectrometry-based analysis. For an in vivo study we used a bioluminescent imaging (BLI)-based orthotopic mouse model of AML, carrying non-targeting, ATP1B1 or ATP1B3 knockout guides. Results: By using CRISPR/Cas9 knockout we could validate ATP1B3 as a selective dependency and performing competitive growth assays we showed that loss of ATP1B3 in ATP1B1 low expressing AML cells leads to synthetic lethality. The absence of both paralogs of the beta subunit results in the loss of their common essential binding partner ATP1A1 in hematologic malignancies, while higher expression of ATP1B1 can stabilize ATP1A1 under the loss of ATP1B3 in solid tumors or in ATP1B1 overexpressing AML cells. Next, we validated our findings in vivo. In a BLI-based orthotopic mouse model of AML, we found that the AML model with ATP1B3 knockout showed lower leukemia burden and normal spleen weight in comparison to a non-targeting or ATP1B1 knockout control. To understand the specific role of ATP1B3 we produced BioID (proximity-dependent biotin identification) constructs for ATP1B1 and ATP1B3. In ongoing studies, through this mass spectrometry-based analysis of protein-protein interactions, we will gain a greater insight into the protein partners of the Na/K-ATP pump. Summary/Conclusion: Taken together, we identified ATP1B3 as a selective dependency in AML. We propose that the elimination of ATP1B3 leads to the destabilization of the sodium-potassium pump when ATP1B1 levels are low, making it a potential tumor-selective therapeutic target for AML and other hematologic malignancies with low expression of ATP1B1.

Na+/HCO3- cotransporter 1 (nbce1) isoform gene expression during smoltification and seawater acclimation of Atlantic salmon.

The life history of Atlantic salmon (Salmo salar) includes an initial freshwater phase (parr) that precedes a springtime migration to marine environments as smolts. The development of osmoregulatory systems that will ultimately support the survival of juveniles upon entry into marine habitats is a key aspect of smoltification. While the acquisition of seawater tolerance in all euryhaline species demands the concerted activity of specific ion pumps, transporters, and channels, the contributions of Na+/HCO3- cotransporter 1 (Nbce1) to salinity acclimation remain unresolved. Here, we investigated the branchial and intestinal expression of three Na+/HCO3- cotransporter 1 isoforms, denoted nbce1.1, -1.2a, and -1.2b. Given the proposed role of Nbce1 in supporting the absorption of environmental Na+ by ionocytes, we first hypothesized that expression of a branchial nbce1 transcript (nbce1.2a) would be attenuated in salmon undergoing smoltification and following seawater exposure. In two separate years, we observed spring increases in branchial Na+/K+-ATPase activity, Na+/K+/2Cl- cotransporter 1, and cystic fibrosis transmembrane regulator 1 expression characteristic of smoltification, whereas there were no attendant changes in nbce1.2a expression. Nonetheless, branchial nbce1.2a levels were reduced in parr and smolts within 2days of seawater exposure. In the intestine, gene transcript abundance for nbce1.1 increased from spring to summer in the anterior intestine, but not in the posterior intestine or pyloric caeca, and nbce1.1 and -1.2b expression in the intestine showed season-dependent transcriptional regulation by seawater exposure. Collectively, our data indicate that tissue-specific modulation of all three nbce1 isoforms underlies adaptive responses to seawater.

Single Artificial Ion Channels with Tunable Ion Transport Based on the Surface Modification of pH-Responsive Polymers.

Artificial ion channels with tunable ionic transport control and intelligent iontronic functions at the nanoscale have a wide application in logic computing and biosensing. Although some artificial ion channels with smart ion transport characteristics have been developed, most of them are constructed on porous membranes with undefined channel numbers. It is still challenging to achieve multiple ion transport features in single nanochannels and to control the ion flow more accurately with excellent repeatability. In this paper, a design strategy is presented to fabricate pH-responsive ion channels with various ion transport features based on a single polydimethylsiloxane (PDMS) nanochannel. The single-ion nanochannel developed by this approach can be further integrated into electronic systems on a chip. Three types of artificial ion channels are demonstrated and investigated systematically in this work. With symmetric or asymmetric pH stimuli, these ion channels can alternatively change their working states among an opened state, a closed state, and an ionic diode state. Four different ion transport features can be realized in a triple-gated ion channel system. With these advantages of the design, it is promising to build smart nanofluidic iontronic devices with widespread applicability in energy conversions, active ion transport control, and biological analysis.

Front Cover: Development of a Core–Shell Heterojunction TiO2/SrTiO3 Electrolyte with Improved Ionic Conductivity (ChemPhysChem 11/2022)

The Front Cover shows the built-in electric field created by the semiconductor heterostructure that confines the proton transport on the surface layer of the nanocomposite core–shell heterostructure imparting faster ion transport and lower activation energy. More information can be found in the Research Article by Jun Wang, Faze Wang and co-workers.

Development of a Core-Shell Heterojunction TiO2 /SrTiO3 Electrolyte with Improved Ionic Conductivity.

The front cover artwork is provided by Prof. Faze Wang's group at the Southeast University. The built-in electric field created by the semiconductor heterostructure confines the proton transport on the surface layer of the nanocomposite core-shell heterostructure imparting faster ion transport and lower activation energy. Read the full text of the Research Article at 10.1002/cphc.202200170.

Toxic effects of the combined cadmium and Cry1Ab protein exposure on the protective and transcriptomic responses of Pirata subpiraticus

Cadmium (Cd) pollution poses a serious threat to agricultural production and paddy field fauna. Crystalline proteins (e.g., Cry1Ab and Cry1Ac) are secreted by Bacillus thuringiensis, which can manage pests via a complicated toxic mechanism and have been widely used for pest control due to the commercialization of transgenic crops (e.g., cotton and rice) that expresses Bt insecticidal proteins. Nonetheless, studies on the effects of combined stress of Cd and Cry1Ab protein on field indicator species are limited. In the present study, we showed that spiders, Pirata subpiraticus, fed with Cd-containing flies+Cry1Ab had dramatically higher Cd accumulation than that in the spiders fed with Cd-containing flies (p < 0.05). In addition, the enrichment of Cd led to the activation of the protective mechanism by elevating the concentrations of glutathione peroxidase, glutathione S-transferase, and metallothionein in the spiders (p < 0.05). An in-depth transcriptome analysis revealed that the activities of ion metal binding proteins, transporters, and channels might play essential roles in the Cd accumulation process. More importantly, the higher Cd concentration in the combined Cd+Cry1Ab exposure prolonged developmental duration of P. subpiraticus, due to the down-regulated cuticle proteins (CPs) encoding genes involved in the molting process, which was regulated by a series of putative transcriptional factors such as ZBTB and zf-C2H2. Collectively, this integrated analysis illustrates that the combined Cd+Cry1Ab exposure increases the adverse effects of Cd stress on the growth, antioxidase, and CPs encoding genes of P. subpiraticus, thus providing a research basis and prospect for the rationality of transgenic Cry1Ab crops in the cultivation of heavy metal contaminated soil.

Establishment of ion channel and ABC transporter assays in 3D-cultured ReNcell VM on a 384-pillar plate for neurotoxicity potential

Neurotoxicity potential of compounds by inhibition of ion channels and efflux transporters has been studied traditionally using two-dimensionally (2D) cultured cell lines such as CHO and HEK-293 overexpressing the protein of interest. However, these approaches are time consuming and do not recapitulate the activity of ion channels and efflux transporters indigenously expressed in neural stem cells (NSCs) in vivo. To overcome these issues, we established ion channel and transporter assays on a 384-pillar plate with three-dimensionally (3D) cultured ReNcell VM and demonstrated high-throughput measurement of ion channel and transporter activity. RNA sequencing analysis identified major ion channels and efflux transporters expressed in ReNcell VM, followed by validating 3D ReNcell-based ion channel and transporter assays with model compounds. Major ion channel activities were measured by specifically inhibiting potassium channels Kv 7.2 with XE-991 and Kv 4.3 with fluoxetine, and a calcium channel with 2-APB. Activities of major efflux transporters, MDR1, MRP1, and BCRP, were assessed using their respective blockers, verapamil, probenecid, and novobiocin. From this study, we demonstrated that 3D-cultured ReNcell VM on the 384-pillar plate could be a good alternative to rapidly identify environmental chemicals and therapeutic compounds for their role in modulating the activity of ion channels and efflux transporters, potentially leading to neurotoxicity.

Bioelectricity Buzz.

Bioelectricity Buzz.

Quadrangular Prism Porous Shells Constructed by Parallelly Interconnected and Lattice‐Strained NiCoP Nanoflakes for Maximized Energy Storage

AbstractOne of the challenges with pseudocapacitive energy storage is maximizing the utilization of active materials while assuring their cycling stability due to diffusion confinement and low electron transferability. Herein, a new insight into the design of architectures with combined advantages of ultrathin 2D materials’ oriented distribution and structural modulation at the atomic scale is proposed. Porous quadrangular prism shells (PQPSs) constructed by parallelly and interconnected lattice‐strained NiCoP nanoflakes are achieved via quadrangular prism‐assisted surface anisotropic growth, template removal, and ion exchange. An aqueous asymmetric supercapacitor with the NiCoP PQPSs and activated carbon (AC) delivers outstanding cycle stability with 103.1% capacity retention even after 30 000 cycles at 20 A g−1, much superior electrochemical performance over that reported for single‐metal phosphides. The NiCoP//AC exhibits a prominent high energy density of 47.7 Wh kg−1 at 800 W kg−1, superior over most state‐of‐the‐art devices. This is mainly attributed to the fact that the nanoflake‐built shells effectively avoid “dead volume,” thus providing abundant ion‐accessible active sites and straight ion transport channels as well as the lattice tensile strain demonstrated by geometrical phase analysis facilitates charge transportation. This work provides an innovative route to the controlled synthesis of space‐oriented phosphides’ arrays for improved energy storage.

Exogenous application of gibberellic acid and silicon to promote salinity tolerance in pea (Pisum sativum L.) through Na+ exclusion

Salinity is a worldwide problem limiting the plant growth and risking food security. This study was conducted to examine exogenous application of silicon (Si), gibberellic acid (GA3) upon the ion transport, growth, yield, and antioxidant enzymes activities of pea plant in saline conditions. Two pea varieties Meteor-FSD and Samrina Zard were pre-treated with GA3 (10-4 M) for 12 h. Plants were allowed to grow with or without silicon in washed silica sand. Ten days old seedlings were shifted in pots with 10 kg soil. Twenty-five days old plants were exposed to 0 and 5 dS m−1 sodium stress. Results showed that exogenous application of GA3 + Si was the best treatment for increasing plant biomass and yield in the presence and absence of NaCl. Furthermore, application of Si or GA3 enhanced chlorophyll content in the leaves, thereby increasing the net assimilation rate of pea varieties under NaCl stress by increasing the antioxidant enzyme activity. Treatment of Si alone or in combination with GA3 significantly reduced Na+ movement in both pea varieties. Results showed that Si has more prominent role than GA3 alone to build-up high plant biomass, yield, soluble protein content and reduction of Na+ transport. Samrina Zard variety showed higher yield, shoot and root dry weight as compared to Meteor-FSD variety in presence and absence of salt. It was concluded that Si can be used as a nutrient for pea under saline or non-saline conditions. Moreover, application of GA3 has a potential role for increasing salinity tolerance, mostly in sensitive pea varieties.

Development of a Core-Shell Heterojunction TiO2 /SrTiO3 Electrolyte with Improved Ionic Conductivity.

Lately, semiconductor-membrane fuel cells (SMFCs) have attained significant interest and great attention due to the deliverance of high performance at low operational temperatures, <550 °C. This work has synthesized the nanocomposite core-shell heterostructure (TiO2 -SrTiO3 ) electrolyte powder by employing the simple hydrothermal method for the SMFC. The SrTiO3 was grown in situ on the surface of TiO2 to form a core-shell structure. A heterojunction mechanism based on the energy band structure is proposed to explain the ion transport pathway and promoted protonic conductivity. The core-shell heterostructure (TiO2 -SrTiO3 ) was utilized as an electrolyte to reach the peak power density of 951 mW cm-2 with an open-circuit voltage of 1.075 V at 550 °C. The formation of core-shell heterostructure among TiO2 and SrTiO3 causes redistribution of charges and establishes a depletion region at the interface, which confined the protons' transport on the surface layer with accelerated ion transport and lower activation energy. The current work reveals novel insights to understand enhanced proton transport and unique methodology to develop low-temperature ceramic fuel cells with high performance.

Light-Controlled Ionic/Molecular Transport through Solid-State Nanopores and Nanochannels.

Biological nanochannels perfectly operate in organisms and exquisitely control mass transmembrane transport for complex life process. Inspired by biological nanochannels, plenty of intelligent artificial solid-state nanopores and nanochannels are constructed based on various materials and methods with the development of nanotechnology. Specially, the light-controlled nanopores/nanochannels have attracted much attention due to the unique advantages in terms of that ion and molecular transport can be regulated remotely, spatially and temporally. According to the structure and function of biological ion channels, light-controlled solid-state nanopores/nanochannels can be divided into light-regulated ion channels with ion gating and ion rectification functions, and light-driven ion pumps with active ion transport property. In this review, we present a systematic overview of light-controlled ion channels and ion pumps according to the photo-responsive components in the system. Then, the related applications of solid-state nanopores/nanochannels for molecular sensing, water purification and energy conversion are discussed. Finally, a brief conclusion and short outlook are offered for future development of the nanopore/nanochannel field.

Recovery from Salinity and Drought Stress in the Perennial Sarcocornia fruticosa vs. the Annual Salicornia europaea and S. veneta.

Current agricultural problems, such as the decline of freshwater and fertile land, foster saline agriculture development. Salicornia and Sarcocornia species, with a long history of human consumption, are ideal models for developing halophyte crops. A greenhouse experiment was set up to compare the response of the perennial Sarcocornia fruticosa and the two annual Salicornia europaea and S. veneta to 30 days of salt stress (watering with 700 mM NaCl) and water deficit (complete withholding of irrigation) separate treatments, followed by 15 days of recovery. The three species showed high tolerance to salt stress, based on the accumulation of ions (Na+, Cl−, Ca2+) in the shoots and the synthesis of organic osmolytes. These defence mechanisms were partly constitutive, as active ion transport to the shoots and high levels of glycine betaine were also observed in non-stressed plants. The three halophytes were sensitive to water stress, albeit S. fruticosa to a lesser extent. In fact, S. fruticosa showed a lower reduction in shoot fresh weight than S. europaea or S. veneta, no degradation of photosynthetic pigments, a significant increase in glycine betaine contents, and full recovery after the water stress treatment. The observed differences could be due to a better adaptation of S. fruticosa to a drier natural habitat, as compared to the two Salicornia species. However, a more gradual stress-induced senescence in the perennial S. fruticosa may contribute to greater drought tolerance in this species.

Osteopontin (OPN)/Secreted Phosphoprotein 1 (SPP1) Binds Integrins to Activate Transport of Ions Across the Porcine Placenta.

Fetal-placental development depends on a continuous and efficient supply of nutrients from maternal blood that are acquired by exchange through the placenta. However, the placenta is a low permeability barrier, and effective transport of substances depends on specific transport mechanisms. Active transport requires that ions or nutrients be moved against an electrical and/or concentration gradient. In pigs, active transport of ions occurs across the chorioallantois placenta to produce an electrochemical gradient that changes throughout gestation. The aim of this study was to utilize Ussing chambers to detect regulation of ion transport across the porcine chorioallantois by a factor(s) within the uterine-placental environment of pigs. For the measurement of transchorioallantoic voltage potential as an index of ion transport across the placenta, pieces of chorioallantoic tissue from Day 60 of gestation were mounted into the cassettes of Ussing chambers, and treatments were added to the mucasal side of the tissue. Treatments included: (1) media incubated with Day 60 chorioallantois (placenta-conditioned media); (2) osteopontin/secreted phosphoprotein 1 (OPN/SPP1) purified from cow's milk; (3) placenta-conditioned media from which OPN/SPP1 was removed; and (4) recombinant rat OPN with an intact RGD integrin binding sequence or a mutated RAD sequence. Ouabain was added to both sides of the chamber. Immunofluorescence was utilized to localize beta 3 integrin, aquaporin 8 and OPN/SPP1 in porcine placental tissues, and OPN/SPP1 within porcine lung, kidney and small intestine. Day 60 chorioallantoic membranes had greater transepithelial voltage in the presence of porcine placenta-conditioned media, indicating that a molecule(s) released from the placenta increased ion transport across the placenta. OPN/SPP1 purified from cow's milk increased ion transport across the placenta. When OPN/SPP1 was removed from placenta-conditioned media, ion transport across the placenta did not increase. Recombinant rat OPN/SPP1 with a mutated RGD sequence that does not bind integrins (RAD) did not increase ion transport across the placenta. Ouabain, an inhibiter of the sodium-potassium ion pump, ablated ion transport across the placenta. The present study documents a novel pericellular matrix role for OPN/SPP1 to bind integrins and increase ion transport across the porcine chorioallantoic placenta.