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PubMed1975

Negative potential level in the outer layer of the toad skin.

The isolated skin of the toad Bufo marinus ictericus when impaled from the outer surface by glass microelectrodes filled with 3 M KCl shows a voltage profile which is a continuous function of the depth of impalement. The superficial intraepithelial potential difference measured with reference to the external solution (PDi) is negative with NaCl-Ringer's solution on both sides of the skin, displaying a minimum of -26.7+/-3.6 mV at 6+/-2 mum. Null value is obtained at 19+/-3 mum, with positive values for deeper impalements. Indications of cell impalements (abrupt voltage and resistance jumps) were frequently observed at sites deeper than 25 mum from the outer surface. Measurements of the electrical resistance between the microelectrode and the external solution, made with single- and double-barreled microelectrodes, showed great discrepancies, which may be attributed to distinct pathways of different resistances in the stratum corneum. PDi measured at a depth of 5 mum was a logarithmic function of Na2SO4 or K2SO4 concentration in the external solution, increasing in negativity with a reduction in concentration. Substitution of Na by K in the external solution had only minor effects on PDi. Acidification of the external solution from pH 9 is accompanied by a reduction in the negative value of PDi. At pH 3 PDi was positive. PDi was interpreted as a diffusion potential at the tip of the microelectrode due to KCl diffusion from the electrode into the matrix of the stratum corneum. Differences in K and Cl mobilities, responsible for the origin of PDi, were attributed to fixed charges in the matrix of the stratum corneum, with density and polarity determined by their degree of proponation, controlled by the hydrogen ion concentration of the external solution. Skin potential, short-circuit current and their relationship to PDI were discussed.

Animals↗
PubMed1990

Nitrate and chloride ions have different permeation pathways in skeletal muscle fibers of Rana pipiens.

The effects of pH on the permeability and conductance of the membranes to nitrate and to chloride of semitendinosus and lumbricalis muscle fibers were examined. Membrane potential responses to quick solution changes were recorded in semitendinosus fibers initially equilibrated in isotonic, high K2SO4 solutions. External solutions were first changed to ones in which either Rb+ or Cs+ replaced K+ and then to solutions containing either NO3- or Cl- to replace SO4(2-). The hyperpolarizations produced by Cl- depend on external pH, being smaller in acid than in alkaline solutions. By contrast, hyperpolarizations produced by NO3- were independent of external pH over a pH range from 5.5 to 9.0. In addition, voltage-clamp measurements were made on short lumbricalis muscle fibers. Initially they were equilibrated in isotonic solutions containing mainly K2SO4 plus Na2SO4. KCl or KNO3 were added to the sulfate solutions and the fibers were equilibrated in these new solutions. When finally equilibrated the fibers had the same volume they had in the sulfate solutions before the additions. Constant hyperpolarizing voltage pulses of 0.6-sec duration were applied when all external K+ was replaced by TEA+. For these conditions, inward currents flowing during the voltage pulses were largely carried by Cl- or NO3- depending on the final equilibrating solution. Cl- currents during voltage pulses were both external pH and time dependent. By contrast, NO3- currents were independent of both external pH and time. The voltage dependence of NO3- currents could be fit by constant field equations with a PNO3 of 3.7.10(-6) cm/sec. The voltage dependence of the initial or "instantaneous" Cl- currents at pH 7.5 and 9.0 could also be fit by constant field equations with PCl of 5.8 x 10(-6) and 7.9 x 10(-6) cm/sec, respectively. At pH 5.0, no measurable "instantaneous" Cl- currents were found. From these results we conclude that NO3- does not pass through the pH, time-dependent Cl- channels but rather passes through a distinct set of channels. Furthermore, Cl- ions do not appear to pass through the channels which allow NO3- through. Consequently, the measured ratio of PCl/PNO3 based on membrane potential changes to ionic changes made on intact skeletal muscle fibres is not a measure of the selectivity of a single anion channel but rather is a measure of the relative amounts of different channel types.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1977

Reconstitution of a proton pump from gastric mucosa.

Purified vesicular fractions from hog gastric mucosa have been incorporated into phosphatidyl serine bilayers. In the presence of MgATP on one side and symmetrical Na2SO4 solutions, a short circuit current (SCC) away from that side is observed increasing exponentially with time, while the corresponding open circuit potential (OCP) is maintained constant for greater than 30 min. In K2SO4 solutions the SCC time course is essentially unchanged, but the OCP falls to almost zero after 15-20 min. In Na -- K gradient there is a similar SCC away from the K-side whose exponential rate is increased by ATP added to both sides. The time course of these events depends only on the time from the formation on the black film. These results are interpreted as showing: (1) There is an ATP-driven proton pump generating a constant potential EH in series with a time dependent conductance gHocekt. (2) There is a shunting K-conductance gKocek't. (3) In the presence of ATP k' greater than k. (4) This time dependence is due to thickness changes in the bilayer. A model relates these results to those obtained with the intact vesicles.

Adenosine Triphosphatases↗
PubMed1978

Studies on chloride permeability of the skin of Leptodactylus ocellatus: III. Na+ and Cl- effect on electrical phenomena.

During their flux through the skin of the frog Leptodactylus ocellatus, Na+ and Cl- interact with each other. This interaction gives rise to electrical phenomena which are studied in the present paper. The skin is mounted in Na2SO4 Ringer's with 115 mM Na+ on the inside, and a variety of outer solutions. The osmolarity of all solutions is kept constant at 237.8 mosmol by adding sucrose. When the main anion used on the outside is SO=4 the electrical potential difference (deltapsi) rises steadily with the concentration of sodium (Na+)0 up to 87 mV, which is reached at about 20 mM. Thereafter deltapsi remains constant. When the main anion is Cl- it is observed that deltapsi rises steadily with (NaCl)0 with a slope similar to the curve obtained with SO=4 (37 mV per decade), but with a lower intercept attributed to an inward Cl pumping which is characteristic of this frog species. At 2--9 mM (NaCl)0 a Cl-specific channel is activated. Further increases of (NaCl)0 produce a decrease of deltapsi. The specificity of the activation of this site by monovalent cations and its use by monovalent anions is also studied.

Animals↗
PubMed1989

Hyperosmolality inhibits exocytosis in sea urchin eggs by formation of a granule-free zone and arrest of pore widening.

Hyperosmolality is known to inhibit membrane fusion during exocytosis. In this study cortical granule exocytosis in sea urchin eggs is used as a model system to determine at what step this inhibition occurs. Strongylocentrotus purpuratus eggs were incubated in hyperosmotic seawater (Na2SO4, sucrose or sodium HEPES used as osmoticants), the eggs activated with 20 microM A23187 to trigger exocytosis, and then quick frozen or chemically fixed for electron microscopy. Thin sections and freeze-fracture replicas show that at high osmolality (2.31 osmol/kg), there is a decrease in cortical granule size, a 90% reduction in granule-plasma membrane fusion, and formation of a granule-free zone between the plasma membrane and cortical granules. This zone averages 0.64 micron in thickness and prevents the majority of granules from docking at the plasma membrane. The remaining granules (approximately 10%) exhibit early stages of fusion which appear to have been stabilized; the matrix of these granules remains intact. We conclude that exocytosis is blocked by two separate mechanisms. First, the granule-free zone prevents granule-plasma membrane contact required for fusion. Second, in cases where fusion does occur, opening of the pocket and dispersal of the granule contents are slowed in hyperosmotic media.

Animals↗
PubMed1988

Influence of serosal Cl on transport properties and cation activities in frog skin.

The effects of serosal substitution of isosmotic Na2SO4-Ringer solution for NaCl-Ringer solution were studied in the short-circuited frog skin (Rana pipiens, Northern variety). Despite prompt changes of transepithelial measurements, initial cellular effects were slight. After 30 to 45 min, however, the transcellular current had decreased and the cell electrical potential had depolarized, in association with decrease of the apical membrane fractional resistance and basolateral membrane conductance. Apical membrane slope conductance was unaffected. Similar effects were obtained with isolated epithelia. With the use of gluconate or NO3 in place of Cl, the effects on cellular current and conductance were minimal or insignificant, despite changes of the cell potential, fractional resistance, and basolateral conductance similar to those seen with sulfate. Following prolonged exposure to serosal SO4-Ringer, the extent of depolarization induced by raising the serosal K concentration decreased, indicating diminution of basolateral K conductance and the existence of other basolateral conductances. Equilibration in serosal gluconate-Ringer enhanced polarization on serosal restoration of Cl or removal of Na, again indicating a time-dependent change in the basolateral conductance pattern. Depolarization on removal of serosal Cl was not attributable to inhibition of the pump. Nor was it the result of decrease of the K equilibrium potential EK: exposure to serosal SO4-Ringer decreased cell K activity aKc from 104 +/- 6 to 58 +/- 4 mM (n = 5), but EK was reduced only slightly; exposure to serosal gluconate increased aKc and EK. Serosal sulfate lowered the cell Na activity aNac, but the electrochemical potential difference for Na across the apical surface was unaffected. The concurrent decrease of both aKc and aNac following serosal substitution of SO4 for Cl raises questions concerning mechanisms of osmoregulation.

Amiloride↗
PubMed1984

Isolation and compositional analysis of secretion granules and their membrane subfraction from the rat parotid gland.

A secretory granule fraction has been isolated from rat parotid by discontinuous gradient centrifugation using hyperosmotic sucrose-Ficoll solutions of low ionic strength. The secretion granule fraction comprises 25% of the total tissue alpha-amylase activity and is judged to be of high purity, both morphologically and by its low level of contamination by enzyme activities associated with other organelles. Secretion granules were lysed by capitalizing on their lability in KCl-containing media, and the low density granule membranes were separated from residual organelle and soluble contaminants by flotation in a sucrose gradient. Residual, poorly extractable secretory contaminants of the granule membrane subfraction were selectively removed by a saponin- (10 micrograms/ml) Na2SO4 (0.3 M) wash, apparently with negligible disruption of granule membrane structure. Based on detailed consideration of the extent of contamination by residual mitochondria and incompletely removed secretory polypeptides, it is possible to estimate that approximately 95% of the protein associated with the purified secretion granule membrane is bona fide granule membrane protein. Further analyses indicate that gamma-glutamyltransferase constitutes a marker enzymatic activity shared by granule membranes and the apical domain of the plasma membrane. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoretograms of radio-iodinated granule membrane polypeptides are characterized by 20-25 radioactive bands of which 5-6 are suggested to be glycoproteins by virtue of their binding of concanavalin A. The limited polypeptide composition of the secretion granule membrane (in comparison to membranes of other cellular compartments) and the high phospholipid-protein ratio (4.4 mg/mg) may reflect the functional specialization of this storage container for secretory proteins.

Animals↗
PubMed1994

Expression of the pea albumin 1 gene in transgenic white clover and tobacco.

In order to improve the quality of pasture protein for ruminant animal nutrition, we are introducing genes encoding rumen-protected proteins, rich in essential amino acids, into white clover (Trifolium repens L.). We have introduced a chimaeric gene transcribed from the 35S CaMV promoter, and encoding the pea albumin 1 (PA1) protein, rich in sulphur amino acids, into the white clover genotype WR8 by Agrobacterium-mediated transformation. A transgenic plant with high levels of PA1 mRNA was crossed with a commercial genotype from cv. Regal Ladino and both the parent and progeny plants were analyzed for expression and accumulation of PA1 gene products. Steady-state mRNA levels and transcript sizes in transgenic parent and progeny were comparable. The abundance and stability of the PA1 protein in transgenic white clover plants was examined by immunoselection of in vivo [35S]Na2SO4-labelled plant proteins. Evidence is presented here, that the 11 kDa PA1 proprotein precursor is processed correctly in petiole tissues of newly regenerated white clover plantlets but only the 6 kDa PA1a subunit accumulates in leaflets of tissue-culture-grown and older glasshouse-grown clover plants. Attempts to enhance PA1 abundance by altering its subcellular target in transgenic tobacco plants suggest that the endomembrane system is a relatively stable environment compared with the cytoplasm or chloroplast, for the accumulation of PA1, despite its low abundance there (< 0.001% total cell protein).

Albumins↗
PubMed1989

HPLC method for quantitation of cholesterol and four of its major oxidation products in muscle and liver tissues.

A fast, sensitive, high performance liquid chromatographic method was developed for the quantitation of cholesterol and four of its major oxidation products: 3 beta-hydroxycholest-5-en-7-one (7-ketocholesterol), cholest-5-ene-3 beta, 7 alpha-diol (7 alpha-hydroxycholesterol), cholest-5-ene-3 beta, 7 beta-diol (7 beta-hydroxycholesterol), and cholest-5-ene-3 beta,25-diol (25-hydroxycholesterol). In this procedure 2:1 chloroform:methanol (v/v) extracts of tissue homogenate were combined, dried over anhydrous Na2SO4, filtered, evaporated to dryness under N2 and dissolved with a mobile phase of either 97:3 or 93:7 hexane:isopropanol (v/v). After membrane filtration and without further purification, aliquots were directly injected onto a 10-microns pore size, 30 X 0.39 cm mu-Porasil normal phase column. The separation of cholesterol and its oxidation products was monitored by a UV detector at 206 and 233 nm. This method was successfully applied to pork muscle as well as mouse liver tissues and was able to detect cholesterol oxidation products (COP) in the ppm range. The identity of the COP was confirmed by mass spectroscopy.

Animals↗
PubMed1975

Effects of some chemical factors on flagellation and swarming of Vibrio alginolyticus.

Vibrio alginolyticus strains recently isolated from Dutch coastal seawater changed flagellar organization when cultivated in the presence of certain chemical agents. On agar media with more than 4.0% (w/v) NaCl the number of lateral flagella per cell decreased with increasing salt concentration. Both on agar media and in broth cultures with 6.0-9.0% (w/v) NaCl, cells with polar tufts of 2-4 sheathed or unsheathed flagella were frequently found. Cells grown on agar media with 7.3-9.8% (w/v) Na2SO4 had drastically reduced numbers of lateral flagella, but lacked polar tufts. EDTA suppressed growth, but did not affect flagellar arrangement. In the presence of 0.1-0.3% boric acid or 0.05-0.1% aluminum hydroxide, cells in liquid media tended to produce lateral, in addition to the polar flagella normally observed in broth cultures. Of a number of surface-active agents tested, Tween 80 and Na-taurocholate, even in high concentrations, did not affect flagellation. Bile salts (0.1%) and Na deoxycholate (0.05%) strongly reduced the number of both polar and lateral flagella. In agar cultures, Na-lauryl sulphate (0.01-0.1%) inhibited the formation of lateral, but increased the incidence of polar flagella. Teepol (0.05-0.2%) had a similar effect and also it had a deteriorating effect on the sheaths of the polar flagella. Concomitant with the reduction in the number of lateral flagella, induced by these agents, swarming on agar media was inhibited.

Agar↗
PubMed2002

Enrichment of iron(III), cobalt(II), nickel(II), and copper(II) by solid-phase extraction with 1,8-dihydroxyanthraquinone anchored to silica gel before their determination by flame atomic absorption spectrometry.

A chelating matrix prepared by immobilizing 1,8-dihydroxyanthraquinone on silica gel modified with 3-aminopropyltriethoxysilane has been characterized by use of cross-polarization magic angle spinning (CPMAS) NMR, diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy, and thermogravimetric analysis and used to preconcentrate Fe(III), Co(II), Ni(II), and Cu(II) before their determination by flame atomic absorption spectrometry. The optimum pH ranges for quantitative sorption are 6.5-8.0, 6.0-7.0, 6.0-8.0, and 7.0-8.5 for Cu, Fe, Co, and Ni, respectively. All the metal ions can be desorbed with 2 mol L(-1) HCl or HNO3. The sorption capacity ( micromol g(-1) matrix) and preconcentration factor were 226.6, 250; 365.6, 300; 101.8, 150; and 109.0, 250 for Cu, Fe, Co, and Ni, respectively. The lowest concentration for quantitative recovery was 4.0, 3.3, 6.6, and 4.0 ng mL(-1), respectively for the four metal ions. The limits up to which electrolytes NaNO3, NaCl, NaBr, Na2SO4, and Na3PO4 and cations Ca(II) and Mg(II) can coexist with the four metal ions during their sorption without adverse effect are reported. The simultaneous enrichment and determination of all the four metals is possible if the total load of metal ions is less than the sorption capacity. Flame AAS was used to determine the metal ions in underground, tap, and river water samples (RSD<or=7.1%) after their enrichment with the matrix. The cobalt content of pharmaceutical samples (multivitamin tablet) preconcentrated by use of this silica gel matrix and determined by FAAS was found to be 2.00 microg g(-1), with RSDtilde;1.7% (reported concentration level, 1.99 microg g(-1)).

Anthraquinones↗
PubMed2006

Electrochemical oxidation of isoniazid catalyzed by (FcM)TMA at the platinum electrode and its practical analytical application.

The electrocatalytic oxidation of isoniazid (INH) by (ferrocenylmethyl)trimethylammonium [(FcM)TMA] at the platinum electrode in 0.10 M Na2SO4 aqueous solution was studied by cyclic voltammetry (CV). Although INH itself showed a very poor electrochemical response at the platinum electrode, the response could be greatly enhanced by using (FcM)TMA as a mediator, which enables a sensitive electrochemical determination of the substrate INH. The reaction rate constant for catalytic oxidation reaction was evaluated as (3.98+/-0.10)x10(3) M(-1) s(-1) by using chronoamperometry (CA). Experimental conditions such as supporting electrolyte and its concentration, solution pH, and the concentrations of the catalyst (FcM)TMA and the substrate INH were investigated to maximize the current efficiency of the electrocatalytic oxidation. The method can be used for the sensitive practical determination of INH, and also opens an avenue for using (FcM)TMA as a mediator in electroanalytical determination which is very simple, cheap, and rapid. Furthermore, no sample pretreatment or time-consuming extraction steps are required prior to the analysis.

Catalysis↗
PubMed2000

Amberlite XAD-7 impregnated with Xylenol Orange: a chelating collector for preconcentration of Cd(II), Co(II), Cu(II), Ni(II), Zn(II) and Fe(III) ions prior to their determination by flame AAS.

A new chelating resin, Xylenol Orange coated Amberlite XAD-7, was prepared and used for preconcentration of Cd(II), Co(II), Cu(II), Fe(III), Ni(II) and Zn(II) prior to their determination by flame atomic absorption spectrophotometry. The optimum pH values for quantitative sorption of Cd(II), Co(II), Cu(II), Fe(III), Ni(II) and Zn(II) are 4.5-5.0, 4.5, 4.0-5.0, 4.0, 5.0 and 5.0-7.0, respectively, and their desorptions by 2 mol L(-1) HCl are instantaneous. The sorption capacity of the resin has been found to be 2.0, 2.6, 1.6, 1.6, 2.6 and 1.8 mg g(-1) of resin for Cd, Co, Cu, Fe, Ni and Zn, respectively. The tolerance limits of electrolytes, NaCl, NaF, NaI, NaNO3, Na2SO4 and of cations, Mg2+ and Ca2+ in the sorption of the six metal ions are reported. The preconcentration factor was between 50 and 200. The t1/2 values for sorption are found to be 5.3, 2.9, 3.2, 3.3, 2.5 and 2.6 min for the six metals, respectively. The recoveries are between 96.0 and 100.0% for the different metals at preconcentration limits between 10 to 40 ng mL(-1). The preconcentration method has been applied to determine the six metal ions in river water samples after destroying the organic matter (if present in very large amount) with concentrated nitric acid (RSD < or = 8%, except for Cd for which it is upto 12.6%) and cobalt content of vitamin tablets with RSD of approximately 3.0%.

Acrylic Resins↗
PubMed2000

Effects of various salts on the determination of arsenic by graphite furnace atomic absorption spectrometry. Direct determination in seawater.

The effect of Na, Mg, Ca and Sr as their nitrate, chloride and sulfate salts and seasalt, with and without the use of palladium, on the determination of arsenic by electrothermal atomic absorption spectrometry was investigated. In the absence of any stabilizing agent, arsenic was partially lost as molecular species at low temperatures. The effect of salts on the shape of the atomization signal, the integrated absorbance and the stabilizing effect were highly dependent both on their nature and mass. By trapping arsenic, oxide species resulting from the decomposition of nitrate salts induced a high stabilization effect depending on their vaporization temperatures: MgO approximately CaO>SrO>Na2O. The stabilization effect of chlorides occurred about 200 degrees C lower and depended on mass, volatility and hydrolytic properties: SrCl2>CaCl2>MgCl2 approximately NaCl. The effect of sulfates was mainly dependent on their decomposition/vaporization mechanisms, and in the presence of Na2SO4 or CaSO4 a strong chemical interference effect was observed. Palladium stabilized arsenic in the presence of nitrates, chlorides or even sulfates, leading to a similar delaying effect, signal shape and integrated absorbance. Seasalt induced also important modifications to the atomization signal of As. Moreover, an interference effect was observed, which could probably be attributed to the simultaneous vaporization of sulfate in seasalt. In seawater, Pd suppressed this interference effect and permitted to use a high pyrolysis temperature up to 1400 C to remove the major part of the seawater matrix before atomization. Under optimized conditions, the detection limit for As obtained in unmodified seawater in the presence of Pd was 0.34 microg L(-1) for a 10 microl sample.

Journal Article↗
PubMed2001

Quinalizarin anchored on Amberlite XAD-2. A new matrix for solid-phase extraction of metal ions for flame atomic absorption spectrometric determination.

Amberlite XAD-2 has been functionalized by coupling it to quinalizarin [1,2,5,8-tetrahydroxyanthraquinone] by means of an -N = N- spacer. Elemental analysis, thermogravimetric analysis, and infrared spectra were used to characterize the resulting new polymer matrix. The matrix has been used to preconcentrate Cu(II), Cd(II), Co(II), Pb(II), Zn(II), and Mn(II) before their determination by flame atomic absorption spectrometry (FAAS). UO2(II) has been preconcentrated for fluorimetric determination. The optimum pH values for maximum adsorption of the metals are between 5.0 and 7.0. All these metal ions are desorbed (recovery 91-99%) with 4 mol L(-1) HNO3. The adsorptive capacity of the resin was found to be in the range 0.94-5.28 mg metal g(-1) resin and loading half-life (t1/2) between 5.3 and 15.0 min. The effects of NaF, NaCl, NaNO3, Na2SO4, Na3PO4, Ca(II), and Mg(II) on the adsorption of these metal ions (0.2 microg mL(-1)) are reported. The lower limits of detection for these metal ions are between 1 and 15.0 microg L(-1). After enrichment on this matrix flame AAS has been used to determine these metal ions (except the uranyl ion) in river water samples (RSD < or = 6.5%); fluorimetry was used to determine uranyl ion in well water samples (RSD < or = 6.3%). Cobalt from pharmaceutical vitamin tablets was preconcentrated by use of this chelating resin and estimated by FAAS (RSD approximately 4%).

Journal Article↗
PubMed1997

The H+ pump in frog skin (Rana esculenta): identification and localization of a V-ATPase.

We here report on studies on the frog skin epithelium to identify the nature of its excretory H+ pump by comparing transport studies, using inhibitors highly specific for V-ATPases, with results from immunocytochemistry using V-ATPase-directed antibodies. Bafilomycin A1 (10 microM) blocked H+ excretion (69 +/- 8% inhibition) and therefore Na+ absorption (61 +/- 17% inhibition after 60 min application, n = 6) in open-circuited skins bathed on their apical side with a 1 mm Na2SO4 solution, "low-Na+ conditions" under which H+ and Na+ fluxes are coupled 1:1. The electrogenic outward H+ current measured in absence of Na+ transport (in the presence of 50 microM amiloride) was also blocked by 10 microM bafilomycin A1 or 5 microM concanamycin A. In contrast, no effects were found on the large and dominant Na+ transport (short-circuit current), which develops with apical solutions containing 115 mm Na+ ("high-Na+ conditions"), demonstrating a specific action on H+ transport. In immunocytochemistry, V-ATPase-like immunoreactivity to the monoclonal antibody E11 directed to the 31-kDa subunit E of the bovine renal V-ATPase was localized only in mitochondria-rich cells (i) in their apical region which corresponds to apical plasma membrane infoldings, and (ii) intracellularly in their neck region and apically around the nucleus. In membrane extracts of the isolated frog skin epithelium, the selectivity of the antibody binding was tested with immunoblots. The antibody labeled exclusively a band of about 31 kDa, very likely the corresponding subunit E of the frog V-ATPase. Our investigations now deliver conclusive evidence that H+ excretion is mediated by a V-ATPase being the electrogenic H+ pump in frog skin.

Animals↗
PubMed1999

Determination of warfarin in waters and human plasma by solid-phase room-temperature transmitted phosphorescence.

A new method for the determination of warfarin in waters and human plasma using solid-phase room-temperature phosphorescence is proposed. The sample was spotted on Whatman No. 4 filter paper, together with iodide and NaOH solutions, after which it was dried and its transmitted phosphorescence intensity measured at 467 nm using two quartz plates to avoid the quenching effect produced by oxygen. The applicable concentration range went from 0.3 to 4.0 mg. L-1, and the detection and quantification limits were 0.08 and 0.28 mg. L-1 respectively. The precision of the method, as a relative standard deviation, was 2.3%. The method was applied in the determination of warfarin in human plasma and different types of water. The interferences produced by the albumin of the human plasma were eliminated by the addition of Na2SO4 saturated solution. Recoveries ranging between 93.0 and 109.0% in the case of water samples, and between 95.0 and 103.0% in the case of human plasma, were obtained. These results were compared with the results obtained by other methods.

Anticoagulants↗
PubMed2002

Growth of sulfate-reducing bacteria with solid-phase electron acceptors.

Hannebachite (CaSO3 x 0.5H2O), gypsum (CaSO4 x 2H2O), anglesite (PbSO4), and barite (BaSO4) were tested as electron acceptors for sulfate-reducing bacteria with lactate as the electron donor. Hannebachite and gypsum are commonly associated with flue gas desulfurization products, and anglesite is a weathering product found in lead mines. Barite was included as the most insoluble sulfate. Growth of sulfate-reducing bacteria was monitored by protein and sulfide (dissolved H2S and HS-) measurements. Biogenic sulfide formation occurred with all four solid phases, and protein data confirmed that bacteria grew under these electron acceptor conditions. Sulfide formation from gypsum was almost comparable in rate and quantity to that produced from soluble sulfate salt (Na2SO4); hannebachite reduction to sulfide was not as fast. Anglesite as the electron acceptor was also reduced to sulfide in the solution phase and galena (PbS) was detected in solids retrieved from spent cultures. Barite as the electron acceptor supported the least amount of growth and H2S formation. The results demonstrate that low-solubility crystalline phases can be biologically reactive under reducing conditions. Furthermore, the results demonstrate that galena precipitation through sulfide production by sulfate-reducing bacteria serves as a lead enrichment mechanism, thereby also alleviating the potential toxicity of lead. In view of the role of acidophilic thiobacilli in the oxidation of sulfides, the present work accentuates the role of anaerobic and aerobic microbes in the biogeochemical cycling of solid-phase sulfates and sulfides.

Biodegradation, Environmental↗