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PubMed1992

The effects of calcium supplementation and exercise on bone density in elderly Chinese women.

A randomized controlled trial was carried out to determine whether calcium supplementation and load-bearing exercise can increase or maintain bone mass in the elderly. Fifty Chinese women, aged 62-92 years, living in a hostel for the elderly in Hong Kong were randomized to enter one of four treatment groups: (I) calcium supplementation of 800 mg (as calcium lactate gluconate) daily; (II) load-bearing exercise four times a week plus a daily placebo tablet; (III) calcium supplementation daily and load-bearing exercise four times a week; (IV) a placebo tablet daily. The interventions went on for 10 months. The bone mineral density (BMD) was measured at three sites in the hip (femoral neck, Ward's triangle and intertrochanteric area) and the L2-4 level of the spine. The percentage change in BMD in 10 months was used as the main outcome measurement. The parathyroid hormone level and indices of bone metabolism were also measured before and after 10 months of intervention. The BMD at Ward's triangle and the intertrochanteric area increased significantly in subjects on calcium supplement (p less than 0.05), but there was no significant change at the spine and femoral neck. Exercise had no effect on bone loss at any site. However, the results of two-way analysis of variance showed a significant joint effect of calcium supplements and exercise at the femoral neck (p less than 0.05), but not at the other sites. The parathyroid hormone levels fell significantly in subjects on calcium supplements (p less than 0.01). Calcium supplement in the form of calcium lactate gluconate was adequately absorbed in elderly Chinese women with a calcium intake of less than 300 mg per day. It was effective in reducing bone loss at the hip, and there may be interaction effects with exercise in maintaining bone density.

Aged↗
PubMed1988

The effects of fetal energy depletion on amniotic fluid concentrations of amino acids, organic acids and related metabolites.

Concentrations of amino and organic acids, phosphate, sulphate, gluconic acid and gluconolactone were measured in amniotic fluid samples which contained either normal or raised hypoxanthine concentrations. In this way, the effect of mild fetal ATP depletion could be determined. The effects of this mild asphyxia were to raise concentrations of phenylalanine, tyrosine, lysine, glycine, phosphate, sulphate, gluconic acid and glucono-1,5-lactone. However, concentrations of a variety of other metabolites were unchanged; thus no diagnostic confusion should arise with organic acidurias in mild asphyxia in contrast to the biochemical mimickry produced by severe asphyxia. Since clinically normal parturition can produce changes in amniotic fluid, urine from newborn or cord blood may not reflect the metabolic balance in utero.

Adenosine Triphosphate↗
PubMed1990

Cl- transport in basolateral renal medullary vesicles: I. Cl- transport in intact vesicles.

This paper provides the results of studies which characterized conductive 36Cl- flux in basolaterally enriched membrane vesicles prepared from rabbit renal outer medulla. Conductive 36Cl- uptake was studied under two different experimental conditions. In the first, 36Cl- flux was driven by an inside positive voltage created with oppositely directed Cl- and gluconate gradients. In the second, an inwardly direct K+ gradient was used to drive 36Cl- uptake. By these two methods, voltage-sensitive 36Cl- uptake was shown to comprise about 45 and 65%, respectively, of the initial rates of total 36Cl- flux. Separate paired studies demonstrated that the conductive 36Cl- uptake was inhibited by the Cl- channel blocker diphenylamine-2-carboxylate (DPC) with an IC50 for DPC of 154 microM. The voltage-dependent 36Cl- uptake had an activation energy of 6.4 kcal/mole. This 36Cl- conductance had an anion selectivity sequence of I- greater than Cl- greater than or equal to NO3- much greater than gluconate.

Animals↗
PubMed1985

Electrogenic calcium transport in plasma membrane of rat pancreatic acinar cells.

ATP-dependent 45Ca2+ uptake was investigated in purified plasma membranes from rat pancreatic acinar cells. Plasma membranes were purified by four subsequent precipitations with MgCl2 and characterized by marker enzyme distribution. When compared to the total homogenate, typical marker enzymes for the plasma membrane, (Na+,K+)-ATPase, basal adenylate cyclase and CCK-OP-stimulated adenylate cyclase were enriched by 43-fold, 44-fold, and 45-fold, respectively. The marker for the rough endoplasmic reticulum was decreased by fourfold compared to the total homogenate. Comparing plasma membranes with rough endoplasmic reticulum, Ca2+ uptake was maximal with 10 and 2 mumol/liter free Ca2+, and half-maximal with 0.9 and 0.5 mumol/liter free Ca2+. It was maximal at 3 and 0.2 mmol/liter free Mg2+ concentration, at an ATP concentration of 5 and 1 mmol/liter, respectively, and at pH 7 for both preparations. When Mg2+ was replaced by Mn2+ or Zn2+ ATP-dependent Ca2+ uptake was 63 and 11%, respectively, in plasma membranes; in rough endoplasmic reticulum only Mn2+ could replace Mg2+ for Ca2+ uptake by 20%. Other divalent cations such as Ba2+ and Sr2+ could not replace Mg2+ in Ca2+ uptake. Ca2+ uptake into plasma membranes was not enhanced by oxalate in contrast to Ca2+ uptake in rough endoplasmic reticulum which was stimulated by 7.3-fold. Both plasma membranes and rough endoplasmic reticulum showed cation and anion dependencies of Ca2+ uptake. The sequence was K+ greater than Rb+ greater than Na+ greater than Li+ greater than choline+ in plasma membranes and Rb+ greater than or equal to K+ greater than or equal to Na+ greater than Li+ greater than choline+ for rough endoplasmic reticulum. The anion sequence was Cl greater than or equal to Br greater than or equal to 1 greater than SCN greater than NO3 greater than isethionate greater than cyclamate greater than gluconate greater than SO2(4) greater than or equal to glutarate and Cl- greater than Br greater than gluconate greater than SO2(4) greater than NO3 greater than 1 greater than cyclamate greater than or equal to SCN, respectively. Ca2+ uptake into plasma membranes appeared to be electrogenic since it was stimulated by an inside-negative K+ and SCN diffusion potential and inhibited by an inside-positive diffusion potential. Ca2+ uptake into rough endoplasmic reticulum was not affected by diffusion potentials. We assume that the Ca2+ transport mechanism in plasma membranes as characterized in this study represents the extrusion system for Ca2+ from the cell that might be involved in the regulation of the cytosolic Ca2+ level.

Adenosine Triphosphate↗
PubMed1978

Evidence for a K+, Na+ permeable channel in sarcoplasmic reticulum.

Potassium and sodium cation permeabilities of skeletal sarcoplasmic reticulum vesicles were characterized by means of 3H-choline, 22Na+ and 86Rb+ isotope efflux and membrane potential measurements. Membrane potentials were generated by diluting K gluconate filled sarcoplasmic reticulum vesicles and liposomes into Tris or Na gluconate media, in the presence or absence of valinomycin, and were measured using the voltage-sensitive membrane probe 3,3'-dipentyl-2,2'-oxacarbocyanine. About 2/3 of the sarcoplasmic reticulum vesicles, designated Type I, were found to be permeable to Rb+, K+ and Na+. The remaining 1/3, Type II vesicles, were essentially impermeable to these ions. The two types of vesicles were impermeable to larger cations such as choline or Tris. Both were present in about the same ratio in fractions derived from different parts of the reticulum structure. Studies with cations of different size and shape suggested that in Type I vesicles permeation was restricted to molecules fitting through a pore with a cross-section of 4--5 A by 6 A or more. When vesicles were sonicated, vesicles permeable to K+ decreased more than those impermeable to K+. These data suggest the existence of K+, Na+ permeable channels which are probably randomly dispersed in the intact reticulum structure at an estimated density of 50 pores/micrometer2. The function of the channel may be to allow rapid K+ movement to counter Ca2+ fluxes during muscle contraction and relaxation.

Animals↗
PubMed1990

Effects of some non-steroidal anti-inflammatory drug copper complexes on polymorphonuclear leukocyte oxidative metabolism.

Interaction between anti-inflammatory drugs and reactive oxygen metabolites must be considered in the course of pharmacological studies intended to develop new compounds. Effects of indomethacin, aspirin, and 3,5-diisopropylsalicylic acid (3,5-DIPS) and their copper complexes on PMNL oxidative metabolism and the evolution of an acute inflammatory reaction were studied in the rat. Experiments were performed in vitro by assessment of superoxide generation and reduction of chemiluminescence by PMNLs incubated or not (control) in medium containing various concentrations of these compounds. A dose-related decrease of these parameters was observed, however, copper complexes were found to be more effective than their parent drugs or Cu gluconate. Copper complexes were also more effective anti-inflammatory agents than their parent ligands or Cu gluconate when the volume of exudate and number of exudate PMNLs were assessed after induction of pleurisy in rats by injection of isologous serum. It is concluded that modulation of the PMNL oxidative burst by copper complexes offers an accounting for the anti-inflammatory activity of these compounds.

Animals↗
PubMed1989

Effects of growth rate and oxygen tension on glucose dehydrogenase activity in Acinetobacter calcoaceticus LMD 79.41.

The regulation of the synthesis of the quinoprotein glucose dehydrogenase (EC 1.1.99.17) has been studied in Acinetobacter calcoaceticus LMD 79.41, an organism able to oxidize glucose to gluconic acid, but unable to grow on both compounds. Glucose dehydrogenase was synthesized constitutively in both batch and carbon-limited chemostat cultures on a variety of substrates. In acetate-limited chemostat cultures glucose dehydrogenase levels and the glucose-oxidizing capacity of whole cells were dependent on the growth rate. They strongly increased at low growth rates at which the maintenance requirement of the cells had a pronounced effect on biomass yield. Cultures grown on a mixture of acetate and glucose in carbon and energy-limited chemostat cultures oxidized glucose quantitatively to gluconic acid. However, during oxygen-limited growth on this mixture glucose was not oxidized and only very low levels of glucose dehydrogenase were detected in cell-free extracts. After introduction of excess oxygen, however, cultures or washed cell suspensions almost instantaneously gained the capacity to oxidize glucose at a high rate, by an as yet unknown mechanism.

Acinetobacter↗
PubMed1999

Hair concentrations of calcium, iron, and zinc in pregnant women and effects of supplementation.

In this investigation, the concentration levels of hair elements of calcium, iron, and zinc were measured in pregnant women from Tianjin metropolis, China. The subjects were 93 cases of pregnant women who had been suffering from calcium, iron, or zinc deficiency judged by blood tests at the mid-term of the second trimester or early in the third trimester. Of these 93 cases, 82 subjects had their hair element levels measured when the blood tests were conducted. Then, they were supplied with mineral element nutrients of gluconic acidic zinc (noted as Zn-nutrient), gluconic acidic calcium (Ca-nutrient), or/and ferrous sulfate (Fe-nutrient) which were correspondent to the deficient element(s) for more than 2 mo before 84 subjects returned to hospital for further diagnoses and had their hair element levels measured for the second time. Finally, in the third trimester or near-parturient phase, 13 subjects had their hair element levels measured again. Except for the deficiencies of calcium, iron, or/and zinc, these subjects were all healthy without symptoms of any diseases. The concentrations of hair Ca, Fe, and Zn were measured by X-ray fluorescence (XRF) spectrometry. These concentrations of the three hair elements measured at three different times were statistically analyzed. From the analyses, it was clear that hair concentrations of Ca, Fe, and Zn could reflect the effects of supplementation. Also, the mutual resistant effects among Ca-, Fe-, and Zn-nutrients were revealed. However, by appropriate combination, the mutual resistant effects could be depressed and mutual promotional effects might be enhanced. Finally, it could be concluded that mineral element deficiencies might be convalesced by adequate compensations of mineral element nutrients.

Calcium↗
PubMed2004

Effect of heme oxygenase-1 inducer hemin on chronic renal failure rats.

The role of HO-1 inducer, hemin, in chronic renal failure (CRF) rats and its possible mechanism of action was studied. 5/6 subtotal nephrectomy was performed to establish chronic renal failure model. Rats were randomly assigned to 4 groups: sham-operated group, CRF group, ferrous gluconate group and hemin group. At the 10th week after operation, serum creatinine, BUN, RBC, HGB and HCT were measured. Renal pathologic changes were observed. RT-PCR and immunohistochemistry were used to detect the expression and distribution of HO-1. RT-PCR and radioimmunoassay was used to determine the expression of ET-1 in the kidney and plasma. The results showed that as compared with CRF group, serum creatinine and BUN in hemin group were reduced significantly and nephrogenic anemia was improved markedly. Glomerular mesangial proliferation and interstitial lesion were also ameliorated significantly. Hemin not only increased the expression of HO-1 but also reduced the expression of ET-1 in the kidney. The level of ET-1 protein in the plasma was also reduced after hemin treatment. Most of these indexes were not obviously changed in ferrous gluconate group. It was suggested that through inducing the expression of HO-1 and reducing the level of ET-1 in the kidney and plasma, hemin plays an important protective role in 5/6 subtotal nephrectomized rats.

Animals↗
PubMed1987

Acute calcium homeostasis in MHS swine.

To elucidate a pathogenesis for the reduction in bone calcium content observed in MHS individuals, we studied the acute calcium homeostasis of MHS swine. This was achieved by the serial measurement, with a calcium selective electrode, of calcium transients in Landrace MHS (five) and control Landrace/large white cross MH negative (five) swine following IV bolus injection of calcium gluconate 0.1 mmol X kg-1--a dose which induced an acute 45 per cent increase in plasma ionised calcium. Experimental animals were anaesthetised with ketamine 10 mg X kg-1 IM, thiopentone (intermittent divided doses) 15-25 mg X kg-1 (total) IV and N2O/O2 (FIO2 0.3) by IPPV to maintain a normal blood gas, acid/base state. The plasma ionised calcium decay curve observed in MHS swine did not differ from that of control normal swine. Further it was noted that the induced acute rise in plasma ionised calcium failed to trigger the MH syndrome in any MHS swine. It is concluded that the mechanisms of acute calcium homeostasis in MHS swine are normal. An explanation for the reduction in bone calcium content observed in MHS individuals must be sought, therefore, through study of the slow long-term component of the calcium regulatory process. In addition, the conventional strictures placed on the use, in MHS patients, of calcium gluconate are called in question.

Anesthesia, General↗
PubMed2004

Hypoparathyroidism and co-existing celiac disease.

A 62-yr-old woman with idiopathic hypoparathyroidism was admitted to our hospital for severe anemia (Hb 5.6 gr/dl) and hypoalbuminemia (3.2 gr/dl). Hypoparathyroidism was diagnosed when she was 33 yr old, because of repeated hypocalcemic tetanic crises, low calcium and high phosphate levels. Since then she has been treated with oral calcium gluconate and calcitriol, with satisfactory clinical balance and normalization of calcium serum levels. After menopause, despite this therapy, the patient still had frequent hypocalcemic tetanic crises, resolving with iv administration, in high doses, of calcium gluconate. The anemia, for which the patient came to our attention, was hypochromic microcytic and in the past she had been treated with iron and transfusion therapy. The patient's recent history also revealed recurrent long lasting episodes of diarrhea, hyporexia and weight loss. The clinical presentation seemed related to a malabsorption syndrome: a celiac disease (CD) diagnosis was confirmed, based upon the finding, at duodenal biopsy, of a severe villous atrophy. A bone mineral density (BMD) evaluation showed a limited reduction of femoral values classified as osteopenia according to the World Health Organization (WHO) criteria. Thereafter, the patient was instructed to follow a gluten-free diet which rapidly led to an improvement of the nutritional parameters and to a reduction of calcium and vitamin D requirements. Difficult clinical and metabolic control in hypoparathyroidism patients may suggest the possible co-existence of both endocrine and extra-endocrine autoimmune diseases, such as CD. Moreover, bone density, normally reduced in celiac patients, seems to be preserved (maintained) by the lack of parathyroid secretion.

Bone Density↗
PubMed2001

Different glycolytic pathways for glucose and fructose in the halophilic archaeon Halococcus saccharolyticus.

The glucose and fructose degradation pathways were analyzed in the halophilic archaeon Halococcus saccharolyticus by 13C-NMR labeling studies in growing cultures, comparative enzyme measurements and cell suspension experiments. H. saccharolyticus grown on complex media containing glucose or fructose specifically 13C-labeled at C1 and C3, formed acetate and small amounts of lactate. The 13C-labeling patterns, analyzed by 1H- and 13C-NMR, indicated that glucose was degraded via an Entner-Doudoroff (ED) type pathway (100%), whereas fructose was degraded almost completely via an Embden-Meyerhof (EM) type pathway (96%) and only to a small extent (4%) via an ED pathway. Glucose-grown and fructose-grown cells contained all the enzyme activities of the modified versions of the ED and EM pathways recently proposed for halophilic archaea. Glucose-grown cells showed increased activities of the ED enzymes gluconate dehydratase and 2-keto-3-deoxy-gluconate kinase, whereas fructose-grown cells contained higher activities of the key enzymes of a modified EM pathway, ketohexokinase and fructose-1-phosphate kinase. During growth of H. saccharolyticus on media containing both glucose and fructose, diauxic growth kinetics were observed. After complete consumption of glucose, fructose was degraded after a lag phase, in which fructose-1-phosphate kinase activity increased. Suspensions of glucose-grown cells consumed initially only glucose rather than fructose, those of fructose-grown cells degraded fructose rather than glucose. Upon longer incubation times, glucose- and fructose-grown cells also metabolized the alternate hexoses. The data indicate that, in the archaeon H. saccharolyticus, the isomeric hexoses glucose and fructose are degraded via inducible, functionally separated glycolytic pathways: glucose via a modified ED pathway, and fructose via a modified EM pathway.

Biodegradation, Environmental↗
PubMed2003

Inhibition of erythrocyte cation channels and apoptosis by ethylisopropylamiloride.

Even though lacking mitochondria and nuclei erythrocytes do undergo apoptotic cell death which is characterized by breakdown of phosphatidylserine asymmetry (leading to annexin binding), membrane blebbing and cell shrinkage. Previously, we have shown that erythrocyte apoptosis is triggered by osmotic shrinkage at least in part through activation of cell volume-sensitive cation channels and subsequent Ca2+ entry. The channels could not only be activated by cell shrinkage but as well by replacement of Cl- with gluconate. Both, channel activity and annexin binding were sensitive to high concentrations of amiloride (1 mM). The present study has been performed to search for more effective blockers. To this end channel activity has been evaluated utilizing whole-cell patch-clamp and annexin binding determined by FACS analysis as an indicator of erythrocyte apoptosis. It is shown that either, increase of osmolarity or replacement of Cl- by gluconate triggers the activation of the cation channel which is inhibited by amiloride at 1 mM but not at 100 microM. Surprisingly, the cation channel was significantly more sensitive to the amiloride analogue ethylisopropylamiloride (EIPA, IC(50)=0.6+/-0.1 microM, n=5). Exposure of the cells to osmotic shock by addition of sucrose (850 mOsm) led to stimulation of annexin binding which was inhibited similarly by EIPA (IC(50)=0.2+/-0.2 microM, n=4). Moreover, annexin binding was inhibited by higher concentrations of HOE 642 (IC(50)=10+/-5 microM, n=5) and HOE 694 (IC(50)=12+/-6 microM, n=4). It is concluded that osmotic shock stimulates a cation channel which participates in the triggering of erythrocyte apoptosis. EIPA is an effective inhibitor of this cation channel and of channel mediated triggering of erythrocyte apoptosis.

Amiloride↗
PubMed2005

Monitoring Cl- movement in single cells exposed to hypotonic solution.

Self-referencing ion--selective electrodes (ISEs), made with Chloride Ionophore I-Cocktail A (Fluka), were positioned 1-3 microm from human embryonic kidney cells (tsA201a) and used to record chloride flux during a sustained hyposmotic challenge. The ISE response was close to Nernstian when comparing potentials (VN) measured in 100 and 10 mM NaCl (deltaVN = 57 +/- 2 mV), but was slightly greater than ideal when comparing 1 and 10 mM NaCl (deltaVN = 70 +/- 3 mV). The response was also linear in the presence of 1 mM glutamate, gluconate, or acetate, 10 microM tamoxifen, or 0.1, 1, or 10 mM HEPES at pH 7.0. The ISE was approximately 3 orders of magnitude more selective for Cl- over glutamate or gluconate but less than 2 orders of magnitude move selective for Clover bicarbonate, acetate, citrate or thiosulfate. As a result this ISE is best described as an anion sensor. The ISE was 'poisoned' by 50 microM 5-nitro-2-(3phenylpropyl-amino)-benzoic acid (NPPB), but not by tamoxifen. An outward anion efflux was recorded from cells challenged with hypotonic (250 +/- 5 mOsm) solution. The increase in efflux peaked 7-8 min before decreasing, consistent with regulatory volume decreases observed in separate experiments using a similar osmotic protocol. This anion efflux was blocked by 10 microM tamoxifen. These results establish the feasibility of using the modulation of electrochemical, anion-selective, electrodes to monitor anions and, in this case, chloride movement during volume regulatory events. The approach provides a real-time measure of anion movement during regulated volume decrease at the single-cell level.

Cell Line↗
PubMed1996

Characterization of whole cell chloride conductances in a mouse inner medullary collecting duct cell line mIMCD-3.

The chloride conductance of inner medullary collecting duct cells (mIMCD-3 cell line) has been investigated using the whole cell configuration of the patch clamp technique. Seventy-seven percent of cells were chloride selective when measured with a NaCl-rich bathing solution and a TEACl-rich pipette solution. Seventy-five percent of chloride-selective cells (90/144) had whole cell currents which exhibited an outwardly-rectifying (OR) current-voltage (I/V) relationship, while the remaining cells exhibited a linear (L) I/V relationship. The properties of the OR and L chloride currents were distinct. OR currents (mean current densities at +/- 60 mV of 66 +/- 5 pA/pF and 44 +/- 3 pA/pF), were time- and voltage-independent with an anion selectivity (from calculated permeability ratios) of SCN- (2.3), NO3- (1.8), ClO4- (1.7), Br- (1.7), I- (1.6), Cl- (1.0), HCO3- (0.5), gluconate- (0.2). Bath additions of NPPB, flufenamate, glibenclamide (all 100 microM) and DIDS (500 microM) produced varying degrees of block of OR currents with NPPB being the most potent (IC50 of approximately 50 microM) while DIDS was the least effective. Linear chloride currents had similar current densities to the OR chloride currents and were also time- and voltage-independent. The anion selectivity sequence was SCN- (2.5), NO3- (1.9), Br- (1.4), I- (1.1), Cl- (1.0), ClO4- (0.5), HCO3- (0.5), gluconate- (0.3). In contrast to the OR conductance, glibenclamide was the most potent and DIDS the least potent blocker of L currents. An IC50 of > 100 microM was observed for NPPB block. Neither OR of L chloride currents were affected by acutely or chronically increased intracellular cAMP and were not affected when intracellular Ca2+ levels were increased or decreased. The molecular identity and physiological role of OR and linear currents in mIMCD-3 cells are discussed.

Animals↗
PubMed1996

An effect of Ca2+ on the Intrinsic Cl(-)-conductance of rat kidney cortex brush border membrane vesicles.

Brush-border membrane vesicles (BBMV) were prepared from superficial rat renal cortex by a divalent(2+)-precipitation technique using either CaCl2 or MgCl2. The dependence of the initial [14C]-D-glucose (or [3H]-L-proline) uptake rate and the extent of the overshoot of D-glucose or L-proline uphill accumulation from solutions containing 100 mM Na+ salt, was found to be dependent upon the precipitating divalent cation. With Mg2+ precipitation the initial uptake and overshoot accumulation of either D-glucose or L-proline were enhanced compared to BBMV prepared by Ca2+ precipitation. When the anion composition of the media was varied (uptake in Cl- media in comparison to gluconate(-)-containing media) it was found that the Cl(-)-dependent component of the initial uptake was markedly depressed with Ca(2+)-prepared BBMV (104.99 +/- 33.31 vs. 13.83 +/- 1.44 pmoles/sec/mg protein for Mg2+ and Ca2+ prepared vesicles respectively). When Ca2+ was loaded into Mg2+ prepared BBMV using a freeze-thaw technique, it was found that the magnitude and Cl- enhancement of D-glucose transport was reduced in a dose-dependent manner. Neomycin, an inhibitor of phospholipase C, had no effect on the reduction of D-glucose uptake by Ca2+ in Mg2+ prepared vesicles. In contrast, phosphatase inhibitors such as vanadate and fluoride were able to partially reverse the Ca2+ inhibition of D-glucose uptake and restore the enhancement due to Cl- media. In addition, inhibitors of protein phosphatase 2B, deltamethrin (50 nM) and trifluoperazine (10 microM), caused partial reversal of Ca2(+)-dependent inhibition of D-glucose uptake. Direct measurement of changes in the bi-ionic (Cl-vs. gluconate-) transmembrane electrical potential differences using the cyanine dye, 3,3'-dipropylthiodicarbocyanine iodide DiSC3-(5) confirmed that Cl- conductance was reduced in Ca(2+)-prepared vesicles. We conclude that a Cl- conductance coexists with Na+ cotransport in rat renal BBMV and this may be subject to negative regulation by Ca2+ via stimulation of protein phosphatase (PP2B).

Amino Acid Sequence↗
PubMed1998

Characterization of calcium-activated chloride channels in patches excised from the dendritic knob of mammalian olfactory receptor neurons.

We investigated the properties of calcium-activated chloride channels in inside-out membrane patches from the dendritic knobs of acutely dissociated rat olfactory receptor neurons. Patches typically contained large calcium-activated currents, with total conductances in the range 30-75 nS. The dose response curve for calcium exhibited an EC50 of about 26 microM. In symmetrical NaCl solutions, the current-voltage relationship reversed at 0 mV and was linear between -80 and +70 mV. When the intracellular NaCl concentration was progressively reduced from 150 to 25 mM, the reversal potential changed in a manner consistent with a chloride-selective conductance. Indeed, modeling these data with the Goldman-Hodgkin-Katz equation revealed a PNa/PCl of 0.034. The halide permeability sequence was PCl > PF > PI > PBr indicating that permeation through the channel was dominated by ion binding sites with a high field strength. The channels were also permeable to the large organic anions, SCN-, acetate-, and gluconate-, with the permeability sequence PCl > PSON > Pacetate > Pgluconate. Significant permeation to gluconate ions suggested that the channel pore had a minimum diameter of at least 5.8 A.

Animals↗
PubMed1998

Interference by carbohydrate substrates, flavonoids, and monosaccharide derivatives on bacterial beta-D-glucuronidase assays.

Most commercially available test kits for water and foodstuffs use beta-galactosidase activity for coliforms and beta-glucuronidase activity for Escherichia coli. We tested the effects on the beta-glucuronidase activity of E. coli W3110 of substances usually present in foods and several synthetic pharmaceutical compounds. Thirteen substances were tested: three carbohydrates, four flavonoids, five monosaccharide derivatives, and dimethyl sulphoxide. In a minimum medium without any other carbon source, glucose (0.1 mM), quercetin (0.1 mM), silymarin (10 mg/L), D-gluconic acid (0.01 mM), D-gluconic acid lactone (0.01 mM), isopropyl-beta-D-thiogalacto pyranoside (1 mM), p-nitrophenyl beta-D-glucuronide (1 mM), and DMSO (1 M) completely inhibited E. coli glucuronidase activity at the above concentrations. However, the following compounds stimulated E. coli glucuronidase activity within the ranges of concentrations shown: glucose (0.0001-0.01 mM), lactose and sucrose (>0.1 mM), D-saccharic acid 1,4 lactone (0.0001-0.1 mM), p-nitrophenyl beta-D-glucuronide (0.001-0.01 mM) and DMSO (2-500 mM). In a rich culture medium that contained other carbon sources (lauryl tryptose broth) E. coli glucuronidase activity in the presence of the extra nutrients was unaffected by the test substances and therefore, under normal conditions in water or foods, they should not interfere with E. coli assays based on measurements of beta-glucuronidase activity.

Biological Assay↗