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This study examined the role of the anal papillae of the freshwater (FW) chironomid larva Chironomus riparius in ionoregulation under ion-poor conditions. The scanning ion-selective electrode technique (SIET) was utilized to characterize the species, direction, and rates of inorganic ion transport by the anal papillae following acute and long-term exposure to ion-poor water (IPW). The major inorganic ions in the hemolymph of larvae treated as above were measured using standard ion-selective microelectrodes. The anal papillae of C. riparius are sites of net NaCl uptake and [H.sup.+] secretion under FW and IPW conditions and are not likely to be a major contributor of [K.sup.+] exchange. Acute and long-term exposure to IPW increased total net transport of [Na.sup.+], [Cl.sup.-], and [H.sup.+] by the anal papillae, but the mechanisms underlying the increase under the two conditions were different. Acute IPW exposure increased the magnitude of net ion fluxes at sites along the anal papillae, while long-term IPW exposure resulted in increased size of the anal papillae with no change in the magnitude of net ion fluxes. The contribution of the anal papillae to observed alterations of hemolymph ion activities upon exposure to IPW is discussed. Inhibitors of the [Na.sup.+]/[H.sup.+] exchangers (EIPA) and carbonic anhydrase (methazolamide) provide evidence for [Na.sup.+]/[H.sup.+] and [C1.sup.-]/HC[O.sub.3.sup.-] exchange mechanisms in the anal papillae. This study demonstrates that C. riparius larvae employ two different mechanisms to upregulate the total net transport of ions by the anal papillae, and these mechanisms are at least partially responsible for regulating hemolymph ion activity. chironomid; anal papilla; transepithelial ion transport; inorganic ions; homeostasis doi: 10.1152/ajpregu.00745.2009.

The Ussing chamber provides a physiological system to measure the transport of ions, nutrients, and drugs across various epithelial tissues. One of the most studied epithelia is the intestine, which has provided several landmark discoveries regarding the mechanisms of ion transport processes. Adaptation of this method to mouse intestine adds the dimension of investigating genetic loss or gain of function as a means to identify proteins or processes affecting transepithelial transport. In this review, the principles underlying the use of Ussing chambers are outlined including limitations and advantages of the technique. With an emphasis on mouse intestinal preparations, the review covers chamber design, commercial equipment sources, tissue preparation, stepby-step instruction for operation, troubleshooting, and examples of interpretation difficulties. Specialized uses of the Ussing chamber such as the pH stat technique to measure transepithelial bicarbonate secretion and isotopic flux methods to measure net secretion or absorption of substrates are discussed in detail, and examples are given for the adaptation of Ussing chamber principles to other measurement systems. The purpose of the review is to provide a practical guide for investigators who are new to the Ussing chamber method. colon; duodenum; ion transport; nutrient absorption

The effects of microgravity on the biophysical properties of frog labyrinthine hair cells have been examined by analyzing calcium and potassium currents in isolated cells by the patch-clamp technique. The entire, anesthetized frog was exposed to vector-free gravity in a random positioning machine (RPM) and the functional modification induced on single hair cells, dissected from the crista ampullaris, were subsequently studied in vitro. The major targets of microgravity exposure were the calcium/potassium current system and the kinetic mechanism of the fast transient potassium current, [I.sub.A]. The amplitude of [I.sub.Ca] was significantly reduced in microgravity-conditioned cells. The delayed current, [I.sub.KD] (a complex of [I.sub.KV] and [I.suib.KCa]), was drastically reduced, mostly in its [I.sub.KCa] component. Microgravity also affected [I.sub.KD] kinetics by shifting the steady-state inactivation curve toward negative potentials and increasing the sensitivity of inactivation removal to voltage. As concerns the [I.sub.A], the I-V and steady-state inactivation curves were indistinguishable under normogravity or microgravity conditions; conversely, [I.sub.A] decay systematically displayed a two-exponential time course and longer time constants in microgravity, thus potentially providing a larger [K.sup.+] charge; furthermore, [I.sub.A] inactivation removal at -70 mV was slowed down. Stimulation in the RPM machine under normogravity conditions resulted in minor effects on [I.sub.KD] and, occasionally, incomplete [I.sub.A] inactivation at -40 mV. Reduced calcium influx and increased [K.sup.+] repolarizing charge, to variable extents depending on the history of membrane potential, constitute a likely cause for the failure in the afferent mEPSP discharge at the cytoneural junction observed in the intact labyrinth after microgravity conditioning. labyrinth; hair cells; microgravity; ionic currents

The vacuole-type ATPases (V-ATPases) are proton pumps in various intracellular compartments of eukaryotic cells. Prokaryotic V-ATPase of Enterococcus hirae, closely related to the eukaryotic enzymes, provides a unique opportunity to study ion translocation by V-ATPases because it transports [Na.sup.+] ions, which are easier to detect by x-ray crystallography and radioisotope experiments. The purified rotor ring (K-ring) of the E. hirae V-ATPase binds one [Na.sup.+] ion per K-monomer with high affinity, which is competitively inhibited by [Li.sup.] or [H.sup.+], suggesting that the K-ring can also bind these ions. This finding is also supported by the K-ring structure at 2.8 [Angstrom] in the presence of [Li.sup.+]. Association and dissociation rates of the [Na.sup.+] to and from the purified K-ring were extremely slow compared with the [Na.sup.+] translocation rate estimated from the enzymatic activity, strongly suggesting that interaction with the stator subunit (I-subunit) is essential for [Na.sup.+] binding to/release from the K-ring. membrane protein | rotary motor | x-ray crystallography | lithium ion Enterococcus hirae

We have used ion-selective electrodes (ISEs) to quantify ion fluxes across giant membrane patches by measuring and simulating ion gradients on both membrane sides. Experimental conditions are selected with low concentrations of the ions detected on the membrane side being monitored. For detection from the cytoplasmic (bath) side, the patch pipette is oscillated laterally in front of an ISE. For detection on the extracellular (pipette) side, ISEs are fabricated from flexible quartz capillary tubing (tip diameters, 2-3 microns), and an ISE is positioned carefully within the patch pipette with the tip at a controlled distance from the mouth of the patch pipette. Transport activity is then manipulated by solution changes on the cytoplasmic side. Ion fluxes can be quantified by simulating the ion gradients with appropriate diffusion models. For extracellular (intrapatch pipette) recordings, ion diffusion coefficients can be determined from the time courses of concentration changes. The sensitivity and utility of the methods are demonstrated with cardiac membrane patches by measuring (a) potassium fluxes via ion channels, valinomycin, and Na/K pumps; (b) calcium fluxes mediated by Na/Ca exchangers; (c) sodium fluxes mediated by gramicidin and Na/K pumps; and (d) proton fluxes mediated by an unknown electrogenic mechanism. The potassium flux-to-current ratio for the Na/K pump is approximately twice that determined for potassium channels and valinomycin, as expected for a 3Na/2K pump stoichiometery (i.e., 2K/charge moved). For valinomycin-mediated potassium currents and gramicidin-mediated sodium currents, the ion fluxes calculated from diffusion models are typically 10-15% smaller than expected from the membrane currents. As presently implemented, the ISE methods allow reliable detection of calcium and proton fluxes equivalent to monovalent cation currents KEY WORDS: ion-selective electrodes * patch clamp * Na/K pump * Na/Ca exchange * proton transport

Fluid and ion secretion in the gallbladder is mainly triggered by the intracellular second messenger cAMP. We examined the action of bile salts on the cAMP-dependent pathway in the gallbladder epithelium. Primary cultures of human gallbladder epithelial cells were exposed to agonists of the cAMP pathway and/or to bile salts. Taurochenodeoxycholate and tauroursodeoxycholate increased forskolin-induced cAMP accumulation to a similar extent, without affecting cAMP basal levels. This potentiating effect was abrogated after PKC inhibition, whereas both taurochenodeoxycholate and tauroursodeoxycholate induced PKC-[alpha] and -[delta] translocation to cell membranes. Consistent with a PKC-mediated stimulation of cAMP production, the expression of six adenylyl cyclase isoforms, including PKC-regulated isoforms 5 and 7, was identified in human gallbladder epithelial cells, cAMP-dependent chloride secretion induced by isoproterenol, a [beta]-adrenergic agonist, was significantly increased by taurochenodeoxycholate and by tauroursodeoxycholate. In conclusion, endogenous and therapeutic bile salts via PKC regulation of adenylyl cyclase activity potentiate cAMP production in the human gallbladder epithelium. Through this action, bile salts may increase fluid secretion in the gallbladder after feeding. [beta]-adrenergic agonist; chenodeoxycholic acid; chloride channels; ursodeoxycholic acid

Synaptotagmin I (Syt I), a low-affinity [Ca.sup.2+]-binding protein, is thought to serve as the [Ca.sup.2+] sensor in the release of neurotransmitter. However, functional studies on the calyx of Held synapse revealed that the rapid release of neurotransmitter requires only approximately micromolar [[Ca.sup.2+]], suggesting that Syt I may play a more complex role in determining the high-affinity [Ca.sup.2+] dependence of exocytosis. Here we tested this hypothesis by studying pituitary cells, which possess high- and low-affinity [Ca.sup.2+]-dependent exocytic pathways and express Syt I. Using patch-clamp capacitance measurements to monitor secretion and the acute antisense deletion of Syt I from differentiated cells, we have shown that the rapid and the most [Ca.sup.2+]-sensitive pathway of exocytosis in rat melanotrophs requires Syt I. Furthermore, stimulation of the [Ca.sup.2+]-dependent exocytosis by cytosol dialysis with solutions containing [micro]M [[Ca.sup.2+]] was completely abolished in the absence of Syt I. Similar results were obtained by the preinjection of antibodies against the CAPS ([Ca.sup.2+]-dependent activator protein for secretion) protein. These results indicate that synaptotagmin I and CAPS proteins increase the probability of vesicle fusion at low cytosolic [[Ca.sup.2+]]. rat melanotrophs; exocytic module; membrane capacitance; calcium sensor

Indicator molecules for caspase-3 activation have been reported that use fluorescence resonance energy transfer (FRET) between an enhanced cyan fluorescent protein (the donor) and enhanced yellow fluorescent protein (EYFP; the acceptor). Because EYFP is highly sensitive to proton ([H.sup.+]) and chloride ion ([Cl.sup.-]) levels, which can change during apoptosis, this indicator's ability to trace the precise dynamics of caspase activation is limited, especially in vivo. Here, we generated an [H.sup.+]- and [Cl.sup.-]--insensitive indicator for caspase activation, SCAT, in which EYFP was replaced with Venus, and monitored the spatio-temporal activation of caspases in living cells. Caspase-3 activation was initiated first in the cytosol and then in the nucleus, and rapidly reached maximum activation in 10 min or less. Furthermore, the nuclear activation of caspase-3 preceded the nuclear apoptotic morphological changes. In contrast, the completion of caspase-9 activation took much longer and its activation was attenuated in the nucleus. However, the time between the initiation of caspase-9 activation and the morphological changes was quite similar to that seen for caspase-3, indicating the activation of both caspases occurred essentially simultaneously during the initiation of apoptosis.

In 1939, A.L. Hodgkin and I found that the nerve action potential shows an `overshoot'--that is, the interior of the fibre becomes electrically positive during an action potential. In 1948, we did our first experiments with a voltage clamp to investigate the current-voltage relations of the nerve membrane. Between those dates, we spent much time speculating about the mechanism by which ions cross the membrane and how the action potential is generated. This article summarizes these speculations, none of which has been previously published.

Research has been conducted on the methyl 4-aryl-5-tosyloxypentanoate and 4-aryl-5-tosylxyhexanoate concomitant. The lactonization of these compounds with a phenyl rearrangement has been investigated and the results are reported.

Research has been conducted on the Tet(L) and Tet(K) proteins. Results indicate that these proteins couple tetracycline-divalent metal efflux to K (super)+ uptake and use this K (super)+ as a coupling ion when external pH increases.

Secondary effects occur as a consequence of previous applications of phosphate to soil. They are caused by the decrease in charge and potential resulting from reaction of phosphate with soil. Such effects on the sorption of newly added phosphate were largest between about pH 3.5 and 5.0. At higher pH, the smaller effects are ascribed to the fact that the potentials are already low and the extra effect of phosphate is small. At lower pH, previously sorbed phosphate was more readily desorbed. It is suggested that this increased lability means that the secondary effects are decreased. Additional keywords: P sorption, P desorption, P buffering., Introduction When specifically sorbed ions react with soil, the charge on the soil is changed. Anions make it more negative; cations more positive. With increasing time, it appears that the [...]

The authors review the publications on electolyte transfer entropies and enthalpies. The topics of interest include the standard molar Gibbs transfer energies of cations between water and mixed aqueous-organic solvents and the compensation which may occur between entropy and enthalpy.

Research has been conducted on the acridine-peptide drug's crystal structure derivatized at carbon 9. The results of the DNA:drug interaction indicate that the acridine intercalates within AA/TT base step and its binding site is located at the sequence's center.

Research has been conducted on the phosphenium ions. The gas-phase reactions of these ions with cis- and trans-1,2-diaminocyclohexanes carried out in a stereoselective manner in a Fourier transform ion cyclotron resonance mass spectrometer are described.

An oxidation process observed in dilute aqueous solutions of ammonia was investigated under steady-state conditions with gold microelectrodes with radii in the range 2.5-30 [micro]m. Over the ammonia concentration range 0.1-10 mM, a well-defined voltammetric wave was observed at ~1.4 V versus Ag/AgCl. It was attributed to the oxidation of hydroxide ions that arise from the dissociation of the weak base. The steady-state limiting current was found to depend on the concentration of supporting electrolyte, and in solution with low electrolyte, it was enhanced by migration contribution, as expected for a negatively charged species that oxidizes on a positively charged electrode. In addition, the steady-state limiting current was proportional to both the ammonia concentration and the electrode radius. The overall electrode process was analyzed in terms of a CE mechanism (homogeneous chemical reaction preceding the heterogeneous electron transfer) with a fast chemical reaction when measurements were carried out in solutions containing N[H.sub.3] at [less than or equal to] 5 mM and with electrodes having a radius of [greater than or equal to] 5 [micro]m. This was ascertained by comparing experimental and theoretical data obtained by simulation. The formation of the soluble complex species Au[(N[H.sub.3]).sub.2.sup.+] was also considered as a possible alternative to explain the presence of the oxidation wave. This process however was ruled out, as the experimental data did not fit theoretical predictions in any of the conditions employed in the investigation. Instead, the direct oxidation of N[H.sub.3], probably to [N.sub.2]O, was invoked to explain the anomalous currents found when the CE process was strongly kinetically hindered. Throughout this study, a parallel was made between the CE mechanism investigated here and that known to occur during the hydrogen evolution reaction from weak acids.

Research has been conducted on the tricyclic marine alkaloid lepadiformine's enantiomer. The stereoselective syntheses of the natural and racemic forms of this enantiomer have been carried out via the use of intramolecular spirocyclization of the N-acyliminium ion with allylsilane and the details are reported.

Research has been conducted on the methylenecyclopropane, bicyclopropylidene and spirocyclopropanated methylenecyclopropanes. The bromine additions to these compound carried out in methanol have been investigated and the results indicate the enhanced bromination rate with the increased number of spiroannelated three-membered rings.

Research has been conducted on the peptide acetals. The results of biocyclization of these acetals via the phenyl group's nucleophilic reaction with endocyclic acyliminium ion are described.

Research has been conducted on the ion pairs with the potassium-hydride and protonic-hydridic bonds. The structure and reactivity of these bonds have been investigated as a function of the phosphine ligand and the details are presented.

The authors review the publications on lanthanide components in the non-oxide glasses chemistry. The topics of interest include chemical preparation, properties and application of non-oxide glasses containing lanthanide ions.

Research has been conducted on the ion conducting solid electrolytes. The topics of interest include solid electrolytes with rear earth as framework elements and as dopants and trivalent cation conductors.

The authors review the publications on organic dye-doped polymers. The topic of interest include the progress on the plastic optical fiber lasers and amplifiers with lanthanides and the design and selection of the chelate materials and plastic optical fiber.

Research has been conducted on the fluoride and alkoxide reagents. The reaction of tetrabutylammonium fluoride with (halomethyl)diphenyl(para-substituted-phenyl)-silanes carried out in tetrahydrofuran and the rearrangement-displacement reaction stereochemistries of optically active (bromomethyl)silane with fluoride and alkoxide reagents are described.

Research has been conducted on the tricyclic carboxylic acids with the angular methano group. The synthesis of these acids mimicking carbapenams and carbapenems carried out via the intramolecular cyclopropanation mediated by the iminium ion and trimethylstannylmethyl group is described.

Research has been conducted on the (S)-profen 2,2,2-triofluoroethyl thioesters. The racemization of these thioesters carried out in isooctane with the trioctylamine as base in investigating the substituents' electron-withdrawing effect to the alpha-phenyl thioester moiety is described.

Research has been conducted on the P4-P6 domain of the Tetrahymena ribozyme. The role of the specific K (super)+ binding sites in P4-P6 folding and stability and the quantitative and site-specific measurements of the P4-P6 ion-linked stability have been investigated and the results are presented.

Research has been conducted on the ionic materials' lattice energy. The estimation of this energy has been carried out via the volume-based approach to the lattice potential energy and the ability of this approach to provide data for the complex ionic materials is discussed.

Research has been conducted on the N-[1-(phenylsulfonyl)alkyl]oxazolidin-2-ones. The preparation and the synthesis of these compounds and their utilization as N-acyliminium ion precursors in the reaction with allyltrimethylsilane are discussed.

Research has been conducted on the radical pairs, radical ions and triplet states occurring in the photosynthesis studied via various EPR techniques. The electronic structure of the photosynthetic reaction center species and their interactions with the protein are described.

Research has been conducted on the chemistry of atmospheres. The use of the mass spectrometry in investigating the neutral and ionic chemistry domain is discussed.

The authors review the publications on the positive atomic ions A (super)+ solvation. The topics of interest include A (super)+ .rare gas diatomic ion interconnections and the physical bonding model in the A (super)+ .rare gas diatomic molecule.

This work was performed as a continuation of ablative laser propulsion (ALP) research recently revived by the authors. An ALP-based space vehicle would be driven by high-energy, short-duration (10-.sup.10] s and less) laser pulses, focused on a solid propellant. Under such irradiation conditions, plasma and laser pulses are temporally separated, and the direct ablation of solid propellant dominates other possible momentum transfer mechanisms. The studies were performed for various elemental targets, ablated at irradiances up to ~3 x [10.sup.13] W/[cm.sup.2] delivered by 100-ps laser pulses at a wavelength of 532 nm. The data, collected predominantly from time-of-flight technique, include ion velocities, number densities, ion density angular distributions, and mass-removal rates. From these data, specific impulses and net momenta exerted on targets by ablation were calculated. For the irradiation conditions used, the highest [I.sub.sp] and lowest mass-removal rates were achieved for low-Z targets, whereas high-Z elements provided higher momenta. The upper limits for [I.sub.sp] derived from ion velocity reached 2 x [10.sup.4]s with carbon (graphite). Ion energies varied from element to element in the range of ~0.4-2.0 keV, with ion fractions of ~0.8-3.8% and mass-removal rates in the range of 0.1-3.0 [micro]g per laser pulse. Ion velocities exhibit Maxwellian distributions, whereas ion number densities in the plasma plume were fitted to a cosine function. All studied characteristics indicate that high-[I.sub.sp] ALP must be based on solid low-Z propellants such as a carbon or aluminum.

Research has been conducted on the benzene chromium tricarbonyl ion. The use of the threshold photoelectron-photoion coincidence spectroscopy and density functional theory calculations in investigating benzene chromium tricarbonyl ion's dissociation kinetics is discussed.

Protein phosphatase type 1 (PP1) is encoded by the essential gene GLC7 in Saccharomyces cerevisiae, glc7-109 (K259A, R260A) has a dominant, hyperglycogen defect and a recessive, ion and drug sensitivity. Surprisingly, the hyperglycogen phenotype is partially retained in null mutants of GAC1, GIP2, and PIG1, which encode potential glycogen-targeting subunits of Glc7. The R260A substitution in GLC7 is responsible for the dominant and recessive traits of glc7-109. Another mutation at this residue, glc7-R260P, confers only salt sensitivity, indicating that the glycogen and salt traits of glc7-109 are due to defects in distinct physiological pathways. The glc7-109 mutant is sensitive to cations, aminoglycosides, and alkaline pH and exhibits increased rates of L-leucine and 3,3'-dihexyloxacarbocyanine iodide uptake, but it is resistant to molar concentrations of sorbitol or KCl, indicating that it has normal osmoregulation. KCl suppresses the ion and drug sensitivities of the glc7-109 mutant. The CsCl sensitivity of this mutant is suppressed by recessive mutations in PMA1, which encodes the essential plasma membrane [H.sup.+] ATPase. Together, these results indicate that Glc7 regulates ion homeostasis by controlling ion transport and/or plasma membrane potential, a new role for Glc7 in budding yeast.