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PubMed2000

Role of p38 in the regulation of renal cortical cyclooxygenase-2 expression by extracellular chloride.

We have previously shown that in renal cortex, COX-2 expression is localized to macula densa and surrounding cortical thick ascending limb of Henle (cTALH). Dietary salt restriction increases local expression of COX-2, which mediates renin production and secretion. Given that decreased luminal chloride [Cl(-)] at the level of the macula densa increases renin production and secretion, we investigated the role of extracellular ion concentration on COX-2 expression. Quiescent rabbit cTALH cells were incubated in a physiological salt solution containing high or low levels of NaCl. Immunoreactive COX-2 expression increased significantly in the low NaCl solution. COX-2 expression also increased after administration of the Na(+)/K(+)/2Cl(-) cotransport inhibitor, bumetanide. Selective substitution of chloride led to increased COX-2 expression, whereas selective substitution of sodium had no effect. The p38 MAP kinase inhibitor PD169316 decreased low NaCl-induced COX-2 expression. Low-salt or low-chloride medium induced cultured cTALH to accumulate >/= 3-fold higher levels of pp38, the activated (phosphorylated) form of p38; low-salt medium also increased pJNK and pERK levels. Feeding rats a low-salt diet for 14 days induced a significant increase in renal cortical pp38 expression, predominantly in the macula densa and cTALH. These results suggest that reduced extracellular chloride leads to increased COX-2 expression, which may be mediated by activation of a p38-dependent signaling pathway.

Animals↗
PubMed1990

Chloride-dependence of amino acid transport in rabbit ileum.

Chloride-dependence of influx across the brush-border membrane of distal rabbit ileum was examined for beta-alanine, 2-methylaminoisobutyric acid (MeAIB), leucine, lysine, proline and D-glucose. Influx of leucine at 2 mM and of D-glucose at 0.5 mM was chloride-independent indicating that substitution of isethionate for chloride has no unspecific effect on sodium gradient driven transport processes. In contrast influx of beta-alanine and MeAIB was totally dependent on the presence of chloride ions. In the absence of chloride, proline transport was reduced to 20% of its control level. This remaining transport can be accounted for by the function of the carrier of alpha-amino-monocarboxylic acids. Transport of leucine at 0.1 mM was reduced by absence of chloride. This is in accordance with the observation of leucine transport by the beta-alanine carrier. The kinetics of chloride and sodium activation of transport of MeAIB were examined at 1 mM MeAIB. Chloride activation was characterized by a Hill coefficient of 1 and a K1/2 of 23.5 mM, and sodium activation by a Hill coefficient of 2 and a K1/2 of 51 mM. Thus cotransport of chloride with an imino acid would be compatible with the known rheogenic nature of this transport. This study adds the imino acid carrier and the beta-alanine carrier to the group of chloride-dependent, epithelial amino acid transport systems.

Amino Acids↗
PubMed2005

Photodegradation of pentachlorophenol and its degradation pathways predicted using density functional theory.

The objectives of the present research were (i) to report the mass balance of chlorine during pentachlorophenol (PCP) photodegradation and (ii) to reveal the photodegradation pathway experimentally with a theoretical proof based on the density functional theory (DFT). The chlorine of PCP was completely mineralized to produce chloride ions after 24h of UV irradiation. As intermediates, 2,3,5,6-tetrachlorophenol, 2,3,4,6-tetrachlorophenol and 2,5-dichlorophenol were identified. At least 80% of the chlorine balance during PCP photodegradation was accounted by PCP, these intermediates, and chloride ions. A DFT calculation showed differences in the C-Cl bond dissociation energy level and the positions of respective PCP molecular and the PCP intermediates. The dechlorination intermediates predicted using the calculated C-Cl bond dissociation energy were consistent with those experimentally confirmed, indicating the feasibility of this theoretical method in predicting the dechlorination pathway.

Forecasting↗
PubMed1979

Diurnal Ion Fluctuations in the Mesophyll Tissue of the Crassulacean Acid Metabolism Plant Mesembryanthemum crystallinum.

Both laboratory- and field-grown Mesembryanthemum crystallinum plants exhibited large scale diurnal ion fluctuations. In mesophyll tissue, potassium and sodium levels varied in conjunction with acid levels while chloride levels varied in opposition. Thus, dark CO(2) fixation in this Crassulacean acid metabolism species seems analogous to the common plant process of malate synthesis to balance cation surplus. Sodium levels in the epidermis appeared to fluctuate in opposition to those in the mesophyll. It is proposed that inorganic cations cycle between mesophyll and epidermal tissue to balance malate accumulation and to produce stomatal opening in the dark.

Journal Article↗
PubMed1998

5-ammoniosalicylic acid chloride monohydrate.

The title compound, C7H8NO3+.Cl-.H2O, crystallized in the centrosymmetric space group P2(1)/c in an ionic form, the proton from HCl having been transferred to the amino N atom. The three H atoms on N, the H atom on the carboxyl group, the H atom of the hydroxyl group and the H atoms of the water molecule, all of which are involved in hydrogen bonding, are ordered. The eight 'best' hydrogen bonds have the following donor-acceptor distances: O...O 2.681 (2) and 2.598 (2); O...Cl 3.367 (1), 3.345 (2) and 3.156 (2); N...O 2.995 (2); N...Cl 3.173 (2) and 3.114 (2) A. In this structure, the acid cations are not linked directly to each other by hydrogen bonds, but are linked indirectly, via hydrogen bonds involving chloride ions and water molecules, into a three-dimensional network. Through basic second-level graphs, finite patterns substantially outnumber chains and rings.

Crystallography, X-Ray↗
PubMed1984

Effects of streptomycin and neomycin on the adrenal medulla of dogs.

The blocking effects of streptomycin and neomycin upon adrenal neurotransmission were studied in dogs. The pressor responses to splanchnic nerve stimulation (SNS) or 50 micrograms/kg nicotine were both blocked by 100 mg/kg but not by 50 mg/kg of the antibiotics injected systemically through the femoral vein. The effect was reversed by intravenous infusion of calcium chloride. The pressor response to SNS, but not that to nicotine, was blocked by the antibiotics injected into the adrenal gland through the adrenolumbar vein at doses up to 10 mg/kg. This effect was reversed by 50 micrograms/kg calcium chloride. Higher doses of antibiotics blocked the response to both stimuli, with only the response to nicotine being reversed by calcium chloride. These data indicate that streptomycin and neomycin block adrenal neurotransmission by interfering with calcium ions at pre- or pre-plus postsynaptic levels depending on the dose and route of administration.

Adrenal Medulla↗
PubMed1993

Steroid hormones and receptors of the GABAA supramolecular complex. I. Benzodiazepine receptor level changes in some extrahypothalamic brain areas of the female rat following sex steroid treatment.

The effects of sex steroid hormones on the different receptor binding sites of the GABAA molecule remain unclear. In this report we have demonstrated, using autoradiography techniques, that the distribution pattern of the benzodiazepine receptors (a component of the GABAA molecule) in some extrahypothalamic brain regions is altered by both in vivo and in vitro sex steroid hormone treatment. In vivo administration of the sex steroids estradiol and progesterone induced a significant change in [3H]flunitrazepam (benzodiazepine agonist) binding levels in the amygdala, and cortico and posterior brain nuclei of the female rat. In fact, elevated and diminished receptor-binding levels were obtained in the corticomedial amygdala nucleus and in the pontine central gray matter respectively, following the administration of estradiol. Significant hormonal effects were also shown for animals that received only a progesterone dose, as demonstrated by the increased and decreased receptor levels in the basolateral amygdala nucleus and cortex lamina VI and in the substantia nigra pars reticulata, respectively. It was interesting, at this point, to investigate whether the hormone effects on [3H]flunitrazepam binding changes might be mediated through a GABA-dependent activity, because the benzodiazepine and GABAA receptors are coupled to a chloride ion channel in an allosteric manner. When 50 microM GABA was added to the incubation medium, substantially altered binding levels were recorded in animals that received progesterone replacement therapy only. The GABA-induced progesterone effects both increased substantially the binding levels in the oriens-pyramidalis CA1 layer of the hippocampus and in the intermediate gray layer of the superior colliculus as well as reducing receptor levels in the substantia nigra pars reticulata.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Pre-clinical trials in Duchenne dystrophy: what animal models can tell us about potential drug effectiveness.

The symptomatic pharmacological therapy of Duchenne dystrophy is poor, glucocorticoids being the sole compounds showing a certain efficacy, although their use is restricted by serious side effects. Pre-clinical trials of prompt-to-use drugs need reliable animal models of the human disease to predict drug effectiveness in patients. The exercised mdx mouse develops a typical pattern of muscle weakness in vivo, which has already been used as an index on which to evaluate drug effectiveness. We have demonstrated that the macroscopic conductance to chloride ion, an index of degeneration-regeneration events occurring in mdx mouse muscles, is specifically impaired by a chronic exercise protocol and is sensitive to the action of in vivo administered drugs acting either by stimulating regeneration (insulin-like growth factor-1 and steroids) or by counteracting calcium-induced degeneration or inflammation (Taurine and steroids). The monitoring of conductance to chloride ion also allows the evaluation of false positive compounds, effective on mouse strength in vivo but not at muscle level, and the functional correlation with other cellular parameters.

Adrenal Cortex Hormones↗
PubMed1988

A microelectrode study of the mechanisms of L-lactate entry into and release from frog sartorius muscle.

1. Changes in intracellular pH and intracellular anion levels were monitored in frog sartorius muscle fibres during exposure to extracellular L-lactate, using ion-sensitive microelectrodes. 2. Resting intracellular pH (pHi) in 20 mmol l-1 HEPES buffer was 7.18 +/- 0.015 (S.E. of mean, n = 62). Exposure to an extracellular solution at pH 6.5 buffered with 20 mmol l-1 3-(N-morpholino)propanesulphonic acid (MOPS) resulted in a slow intracellular acidification. 3. A reversible decrease in pHi and an increase in intracellular anion levels was observed when L-lactate replaced chloride in equimolar amounts. The increase in intracellular anion level is consistent with intracellular accumulation of L-lactate ion. 4. The rate and steady-state change in pHi and anion level was a function of both extracellular pH and L-lactate concentration, providing evidence for the coupled movement of lactate and proton equivalents. 5. The initial rate of uptake of L-lactate, as measured by the change of pHi, was a non-linear function of the extracellular L-lactate concentration at extracellular pH 6.8 and 7.35. 6. No saturation was observed with concentrations of L-lactate between 5 and 60 mmol l-1 at pH 7.35 and 2.5 and 40 mmol l-1 at pH 6.8. 7. The non-linear relationship between the initial rate of change in pHi and extracellular L-lactate was well fitted by a curve defining uptake as the sum of a carrier process displaying Michaelis-Menten kinetics and a passive diffusion component. The apparent Km of the carrier was 10 mmol l-1 at pHo 7.35 and 4 mmol l-1 at pHo 6.8. 8. The initial rate of change of pHi in the presence of L-lactate was significantly inhibited 39.1 +/- 6.2% by 2-5 mmol l-1 alpha-cyano-4-hydroxycinnamate (n = 9; P less than 0.05, paired t test). 9. alpha-Cyano-4-hydroxycinnamate had no detectable effect on the initial rate of change of pHi induced by propionate exposure. 10. The initial rate of change of pHi induced by L-lactate was not affected by 20-100 mumol l-1 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid (SITS). 11. We conclude that L-lactate crosses the membrane of the frog sartorius muscle with proton equivalents via (1) a carrier-mediated process, and (2) passive diffusion of lactic acid. In the physiological range of L-lactate concentrations and pH the transport process dominates.

Animals↗
PubMed1982

Chloride activity and its control in skeletal and cardiac muscle.

Ion-selective microelectrodes have been used to compare the mechanisms controlling intracellular Cl- activity in skeletal and cardiac muscle. In frog Sartorius skeletal muscle fibres, Cl- levels are low (about 3 mM) and are determined mainly passively. The effect of any Cl- transport system will be quickly short-circuited through the high membrane Cl- conductance. In contrast, the sheep-heart Purkinje fibre, like other cardiac tissues, contains higher than passive levels of intracellular Cl- (20-30 mM). Many Cl- movements occur, not through Cl- channels (the permeability for Cl- is low), but by a Cl- -HCO3- countertransport system. High internal Cl- levels are achieved by an exchange of extracellular Cl- for intracellular HCO3-, which acidifies the fibre by 0.3 pH. Anion exchange in heart differs from that proposed for other excitable cells in that it is not specialized to compensate for an intracellular acidosis. Instead, it can prevent the fibres from becoming too alkaline by promoting a bicarbonate efflux and a chloride influx whenever internal bicarbonate levels rise. Possible reasons for this are briefly discussed.

Animals↗
PubMed1990

Biotoxicity of mercury as influenced by mercury(II) speciation.

Integration of physicochemical procedures for studying mercury(II) speciation with microbiological procedures for studying the effects of mercury on bacterial growth allows evaluation of ionic factors (e.g., pH and ligand species and concentration) which affect biotoxicity. A Pseudomonas fluorescens strain capable of methylating inorganic Hg(II) was isolated from sediment samples collected at Buffalo Pound Lake in Saskatchewan, Canada. The effect of pH and ligand species on the toxic response (i.e., 50% inhibitory concentration [IC50]) of the P. fluorescens isolated to mercury were determined and related to the aqueous speciation of Hg(II). It was determined that the toxicities of different mercury salts were influenced by the nature of the co-ion. At a given pH level, mercuric acetate and mercuric nitrate yielded essentially the same IC50s; mercuric chloride, on the other hand, always produced lower IC50s. For each Hg salt, toxicity was greatest at pH 6.0 and decreased significantly (P = 0.05) at pH 7.0. Increasing the pH to 8.0 had no effect on the toxicity of mercuric acetate or mercuric nitrate but significantly (P = 0.05) reduced the toxicity of mercuric chloride. The aqueous speciation of Hg(II) in the synthetic growth medium M-IIY (a minimal salts medium amended to contain 0.1% yeast extract and 0.1% glycerol) was calculated by using the computer program GEOCHEM-PC with a modified data base. Results of the speciation calculations indicated that complexes of Hg(II) with histidine [Hg(H-HIS)HIS+ and Hg(H-HIS)2(2+)], chloride (HgCl+, HgCl2(0), HgClOH0, and HgCl3-), phosphate (HgHPO4(0), ammonia (HgNH3(2+), glycine [Hg(GLY)+], alanine [Hg(ALA)+], and hydroxyl ion (HgOH+) were the Hg species primarily responsible for toxicity in the M-IIY medium. The toxicity of mercuric nitrate at pH 8.0 was unaffected by the addition of citrate, enhanced by the addition of chloride, and reduced by the addition of cysteine. In the chloride-amended system, HgCl+, HgCl2(0), and HgClOH0 were the species primarily responsible for observed increases in toxicity. In the cysteine-amended system, formation of Hg(CYS)2(2-) was responsible for detoxification effects that were observed. The formation of Hg-citrate complexes was insignificant and had no effect on Hg toxicity.

Biological Assay↗
PubMed2006

Influences of carbonate and chloride ions on persulfate oxidation of trichloroethylene at 20 degrees C.

Application of in situ chemical oxidation (ISCO) involves application of oxidants to contaminants such as trichloroethylene (TCE) in soil or groundwater in place. Successful application of ISCO at a hazardous waste site requires understanding the scavenging reactions that could take place at the site to better optimize the oxidation of target contaminants and identification of site conditions where ISCO using persulfate may not be applicable. Additionally, estimation of the oxidant dose at a site would need identification of groundwater constituents such as alkalinity and chlorides that may scavenge radicals and therefore use up the oxidant that is targeted for the contaminant(s). The objective of this study was to investigate the influence of various levels of chloride and carbonates on persulfate oxidation of TCE at 20 degrees C under controlled conditions in a laboratory. Based on the results of the laboratory experiments, both chloride and alkalinity were shown to have scavenging effects on the rate of oxidation of TCE. It was found that at a neutral pH, persulfate oxidation of TCE was not affected by the presence of bicarbonate/carbonate concentrations within the range of 0-9.20 mM. However, the TCE degradation rate was seen to reduce with an increase in the level of carbonate species and at elevated pHs. TCE degradation in the presence of chlorides revealed no effect on the degradation rate especially at chloride levels below 0.2 M. However, at chloride levels greater than 0.2 M, TCE degradation rate was seen to reduce with an increase in the chloride ion concentration. Prior to application of persulfate as an oxidant, a site should be screened for the presence of scavengers to evaluate the potential of meeting target cleanup goals within a desirable timeframe at the site.

Carbonates↗
PubMed2005

[Determination of sodium chlorite in processed herring roe by ion chromatography with a conductivity detector].

An analytical method for residual sodium chlorite in several kinds of processed herring roe treated with sodium chlorite was studied. Sodium chlorite was extracted with 9 mmol/L sodium carbonate. After centrifugation, the supernatant was filtered through a 0.2 microm nylon filter. The filtrate was deproteinized by ultrafiltration and chloride ion was removed with an On-Guard Ag cartridge column. The eluate was subjected to conductivity detector-ion chromatography. Recoveries of sodium chlorite from herring roe spiked at the level of 5 mg/kg were 88 +/- 3.7% (n = 5, CV 4.2%). The method had a quantitation limit of 5 mg/kg for processed herring roes.

Chlorides↗
PubMed2003

Spatial patterns of nitrate, chloride, sulfate, and fluoride concentrations in the Woodbine Aquifer of north-central Texas.

A geographic information system was used to map and analyze nitrate, chloride, sulfate, and fluoride concentrations in 110 wells tapping the Woodbine Aquifer. The study area, covering nine counties in north-central Texas, includes large percentages of both urban and agricultural land uses. Land use maps were compared with solute concentration data, and statistics were applied to detect associations between solutes, well depth, and land use. Anthropogenic sources such as fertilizer applications and natural sources such as gypsum, lignite, and clay deposits controlled nitrate, chloride, and sulfate concentrations, each inversely correlated with well depth. However, only one nitrate observation--from a shallow well in the aquifer's outcrop zone--surpassed the maximum contaminant level (MCL) of 44.3 mg L(-1). By comparison, nearly half of the sulfate and several of the chloride observations surpassed the MCL of 250 mg L(-1) for each of those ions. Volcanic ash deposits influenced fluoride concentrations, which directly correlated with well depth. There were no statistically significant associations between solute concentrations and land use. Low recharge rates and confining layers have mitigated anthropogenic impacts on solute levels in the aquifer.

Chlorides↗
PubMed1995

Induction of endogenous channels by high levels of heterologous membrane proteins in Xenopus oocytes.

Xenopus oocytes are widely employed for heterologous expression of cloned proteins, particularly electrogenic molecules such as ion channels and transporters. The high levels of expression readily obtained permit detailed investigations without interference from endogenous conductances. Injection of min K mRNA into Xenopus oocytes results in expression of voltage-dependent potassium-selective channels. Recent data show that injections of high concentrations of min K mRNA also induce a chloride current with very different biophysical, pharmacological, and regulatory properties from the min K potassium current. This led to the suggestion that the min K protein acts as an inducer of endogenous, normally silent oocyte ion channels. We now report that high levels of heterologous expression of many membrane proteins in Xenopus oocytes specifically induce this chloride current and a hyperpolarization-activated cation-selective current. The current is blocked by 4,4'-diisothiocyanostilbene-2-2'-disulphonic acid and tetraethylammonium, enhanced by clofilium, and is pH-sensitive. Criteria are presented that distinguish this endogenous current from those due to heterologous expression of electrogenic proteins in Xenopus oocytes. Together with structure-function studies, these results support the hypothesis that the min K protein comprises a potassium-selective channel.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2002

Complete characterisation of Tn5530 from Burkholderia cepacia strain 2a (pIJB1) and studies of 2,4-dichlorophenoxyacetate uptake by the organism.

The complete genetic characterisation of Tn5530 in Burkholderia cepacia strain 2a (pIJB1) has been accomplished, indicating that it is a Tn3-like transposon with a complex structure bearing operons for the catabolism of 2,4-dichlorophenoxyacetate (2,4-D) and malonate. Tn5530 is terminated at both ends by the IS1071::IS1471 element and the 2,4-D- and malonate-dissimilatory operons are separated by a region encoding a putA and lrp gene and a gene encoding a chloride channel protein. The chloride channel protein may have a role in the expulsion of chloride ions liberated by the dissimilation of 2,4-D. In addition, a putative transposase with a high level of sequence similarity to those of plasmid pGH1 from Xanthomonas campestris pv. vesicatoria and Pseudomonas syringae pv. glycinea, and a transcription factor similar to those of the TetR family with low but significant levels of sequence similarity to those identified in a number of other organisms was observed. The entire Tn5530 sequence length, including the IS1071::IS1471 elements, was found to be 40,956bp, and pIJB1 was replicon-typed and otherwise characterised as being of the IncP-1beta subgroup, bearing merA and merD genes conferring resistance to mercuric chloride. The rate of uptake of 2,4-D by B. cepacia strain 2a was observed to proceed more readily at acid pH, suggesting involvement of the undissociated form of the compound. Uptake did not show saturation kinetics, was concentration-dependent, and appeared to occur in two stages; an initial accumulation followed by a linear second phase. Uptake could be inhibited by sodium azide but not by arsenate, N,N(')-dicyclohexylcarbodi-imide (DCCD) or carbonylcyanide m-chlorophenyl-hydrazone (CCCP) suggesting that it is not energy-dependent.

2,4-Dichlorophenoxyacetic Acid↗