Kisspeptin promotes follicular development through its effects on modulation of P450 aromatase expression and steroidogenesis in sheep ovarian follicles.

The present study was conducted to ascertain whether the role of kisspeptin in promoting in vitro development of preantral follicles was through the regulation of P450 aromatase gene expression and steroidogenesis in sheep. Accordingly, the cumulus cells and oocytes were collected from different development stages of preantral follicles grown in vivo and cultured in vitro in TCM199B (Group I), TCM199B + KP (10 µg/mL) (Group II) and Standard medium + KP (10 µg/mL). To measure the steroid (Estradiol-17ß; E2 and Progesterone; P4 ) synthesis through ELISA, spent culture medium was collected separately from the same in vitro groups. E2 synthesis in the spent medium collected from all the three groups showed an increasing trend from PFs' exposed to respective culture media for 3 min to 2-day culture stage but decreased thereafter till 6-day culture stage. This is followed by a sharp increase in E2 concentration in the spent medium collected after in vitro maturation. However, P4 synthesis in group III followed increased pattern as the development progressed from PFs' exposed to culture medium for 3 min to in vitro maturation stage. The steroid production was observed at all stages of in vitro development in altered supplemented conditions. The steroid synthesis in the spent medium was highest in the 6 day cultured PFs' in Standard medium + KP matured in vitro for 24 h. Therefore, supplementation of kisspeptin along with other growth factors promoted steroid production in cultured preantral follicles far better than in other media.

Identification of second arginine-glycine-aspartic acid motif of ovine vitronectin as the complement C9 binding site and its implication in bacterial infection.

Vitronectin (Vn), a multifunctional protein of blood and extracellular matrix, interacts with complement C9. This interaction may modulate innate immunity. Details of Vn-C9 interactions are limited. Vn-C9 interactions were assessed by employing a goat homologous system and observing Vn binding to C9 in three different assays. Using recombinant fragments, C9 binding was mapped to the N-terminus of Vn. Site directed mutagenesis was performed to alter the second arginine glycine aspartic acid (RGD) sequence (RGD-2) of Vn. Changing R to G or D to A in RGD-2 caused significant decrease in Vn binding to C9 whereas changing of R to G in the first RGD motif (RGD-1) had no effect on Vn binding to C9. These results imply that the RGD-2 of goat Vn is involved in C9 binding. In a competitive binding assay, the presence of soluble RGD peptide inhibited Vn binding to C9 whereas heparin had no effect. Vn binding to C9 was also evaluated in terms of bacterial pathogenesis. Serum dependent inhibition of Escherichia coli growth was significantly reverted when Vn or its N-fragment were included in the assay. The C-fragment, which did not support C9 binding, also partly nullified serum-dependent inhibition of bacterial growth, probably through other serum component(s).

Dual optoelectronic visual detection and quantification of spectroscopically silent heavy metal toxins: a multi-measurand sensing strategy based on Rhodamine 6G as chromo or fluoro ionophore.

A novel colorimetric chemo-sensor for the simultaneous visual detection and quantification of spectroscopically silent heavy metal toxins viz. cadmium, lead and mercury has been developed. This is based on the proposed sequential ligand exchange (SLE) mechanism of iodide from Pb-I(-)-Rhodamine 6G ion associate with citrate (without affecting ion associates of Cd and Hg) and subsequently from Cd-I(-)-Rhodamine 6G ion associate with EDTA (without affecting Hg-I(-)-Rhodamine 6G). Multi-measurand detection and quantification by colorimetry is possible as the individual toxins gives identical bathochromic shifts in aqueous solution, i.e. from 530 to 575 nm on formation of ternary ion associates in singular, binary and ternary mixtures. The visual detection provides a simple, quick and sensitive detection method in addition to quantification via spectrophotometry with Sandell sensitivities of 1.1, 15 and 2.5 microg dm(-2) for cadmium, lead and mercury, respectively. The developed procedure has been successfully tested for the analysis of environmental (cast alkali, lead acid battery and zinc manufacturing industry effluents) samples. Furthermore, the multi-measurand quantification of the above-mentioned heavy metal toxins based on fluorescence quenching and use of Pyronine G as chromo-ionophore instead of Rhodamine 6G is also described.

Chemical switch based reusable dual optoelectronic sensor for nitrite.

An optical sensor was developed for sensing of nitrite based on the monotonous decrease in absorbance of Rhodamine 6G at 525 nm (the absorbance maximum of dye) with increasing concentration of nitrite. This sensor also permits naked eye detection. Various parameters like concentrations of sulphuric acid and Rhodamine 6G, response time and stability were varied and optimal conditions are reported. Under these conditions, the developed sensor enables the determination of nitrite in the concentration range 0-12.18 micromol L(-1). The nitrite response is selective as 60-2.5x10(5) fold amounts of several anions and cations have no deleterious effect. The addition of nitrite to Rhodamine 6G dye causes hypsochromic shift from 525 to 385 nm while several other anions like I(-), SCN(-), ClO(4)(-), [HgI(4)](2-) and [Zn (SCN)(4)](2-) showed a bathochromatic shift from 525 to 575 nm. The sequential addition of nitrite and sulphamic to Rhodamine 6G in 0.75 mol L(-1) sulphuric acid solution results in switching of "ON" and "OFF" absorbance. The time elapse and concentration of sulphamic acid required for chemical switching was also established. Similar "ON" and "OFF" switching behaviour was observed in fluorescence studies also. This enabled the design and development of reusable chemical switch based dual optoelectronic sensor, for monitoring of traces of nitrite in environmental and food samples. The plausible mechanism for above switching behaviour is also proposed.

Potentiometric transducer based biomimetic sensors for priority envirotoxic markers--an overview.

Most of the potentiometric sensing electrodes offer detection limits of the order of approximately 1 micromol L(-1) rarely stretching down to 0.1 micromol L(-1). Recent advances have made it possible to bring these levels down to 0.01-10 nmol L(-1) for some inorganic ions. Most of these electrodes (barring a few) have come up to expectations in terms of selectivity in spite of significant strides made in the design and synthesis of novel chemical receptors. Imprinted polymers or plastic antibodies which rely on lock and key mechanism can, in principle, selectively rebind and sense a particular analyte in a host of other analogous species of similar size, shape and geometry. Thus, the integration of imprinted polymers with potentiometric transducers has immense potentialities in the fabrication of commercial sensing devices. This review gives an overview of research efforts made so far in this direction, critically discusses the virtues and vices and presents the futuristic scenario on imprinted polymer based potentiometric sensors.

Design of two-dimensional biomimetic uranyl optrode and its application to the analysis of natural waters.

A two-dimensional biomimetic optrode for the detection and quantification of uranium in natural waters was fabricated. The sensing element was designed by the inclusion of uranyl ion imprinted polymer particles into polymethyl methacrylate followed by casting a thin film on a glass slide without any plasticizer. The ion imprinted polymer material was prepared via covalent immobilization of the newly synthesised ligand 4-vinyl phenylazo-2-naphthol by thermal polymerization. Operational parameters such as pH, response time and the amount of sensing material were optimized. The response characteristics of the imprinted and the corresponding non-imprinted polymer inclusion optrodes of uranium were compared under optimum conditions. The imprinted polymer inclusion optrode responds linearly to uranium in the concentration range 0-1.0 microg mL(-1) with a detection limit of 0.18 microg mL(-1), which is much better than the solution studies using 4-vinyl phenylazo-2-naphthol (1.5 microg mL(-1)). Triplicate determinations of 100 microg of uranium(VI) present in 250 mL of solution gave a mean absorbance of 0.018 with a relative standard deviation of 8.33%. The superior sensitivity of imprinted polymer inclusion optrode is exemplified by lower detection limits and broader dynamic range over non-imprinted polymer inclusion optrode. The developed imprinted polymer inclusion optrode was found to give stable and precise response for 3 months and can be used without any loss in sensitivity. The applicability for analysing ground, lake and tap-water samples collected in the vicinity of uranium deposits was successfully demonstrated.

Dithiocarbamate functionalized or surface sorbed Merrifield resin beads as column materials for on line flow injection-flame atomic absorption spectrometry determination of lead.

This article describes the preparation of dithiocarbamate immobilized/functionalized and diethylammonium dithiocarbamate (DDTC) sorbed Merrifield Chloromethylated Resin (MCR) beads and comparison of these materials for on-line flow injection (FI)-flame atomic absorption spectrometry (FAAS) determination of lead. The above two materials enrich lead quantitatively over an identical optimal pH range (8.0-9.0), a preconcentration/loading time (up to 4 min) and elution with acidified methanol (a minimum of 0.01 molL(-1) HNO(3) in methanol). However, the detection limit for lead using dithiocarbamate functionalized MCR beads is 1.3 microgL(-1) compared to 3 microgL(-1) for DDTC sorbed MCR beads. Again, the sensitivity enhancement over direct FAAS signal is 48- and 27-fold, respectively. In addition, dithiocarbamate functionalized MCR beads offers better precision compared to DDTC sorbed MCR beads as the corresponding relative standard deviation (R.S.D.) values for five successive determinations of 0.20 microgmL(-1) are 1.44 and 4.36%, respectively. The accuracy of the developed on-line FI-FAAS procedure employing dithiocarbamate functionalized MCR beads as column material was tested by analyzing Certified Reference Material (CRM) of soil (IAEA soil-7) and marine sediment reference material (MESS-3) supplied by International Atomic Energy Agency (IAEA), Vienna and National Research Council (NRC), Canada, respectively. Furthermore, the developed procedure has been successfully tested for the analysis of surface, pond, ground and effluent water and soil samples collected from the vicinity of lead acid battery industry in India.

Investigation of the role of chelating ligand in the synthesis of ion-imprinted polymeric resins on the selective enrichment of uranium(VI).

Uranyl ion-imprinted polymeric (IIP) resins were prepared by dissolving stoichiometric amounts of uranyl nitrate and selected chelating ligands, viz. salicylaldoxime, catechol, succinicacid, 5,7-dichloroquinoline-8-ol and 4-vinyl pyridine in 2-methoxy ethanol (porogen) and copolymerizing thermally in the presence of 2-hydroxyethylmethacrylate (HEMA) and ethyleneglycol-dimethacrylate (EGDMA), using 2,2'-azobisisobutyronitrile (initiator). Again, IIP resins were also prepared on similar lines by utilizing ternary [uranium-non-vinylated ligand-vinylated ligand (4-vinyl pyridine)] complexes. Non-imprinted polymeric resins were identically prepared in both cases without the use of uranyl imprint ion. The percent enrichment and retention capacity studies showed significant imprinting effect in all cases. However, ion-imprinted polymeric resins formed with succinic acid (SA) or 5,7-dichloroquinoline-8-ol (DCQ) and 4-vinylpyridine (VP) alone gave quantitative enrichment and various parameters that influence the enrichment and elution were then optimized. The percent enrichment of uranium from synthetic seawater solutions was found to be 25.0+/-0.5 and 83.0+/-0.8 for SA-VP and DCQ-VP systems, respectively. The DCQ-VP-based IIP resins were successfully tested for the recovery of uranium from real seawater samples.

Amberlite XAD-4 functionalized with succinic acid for the solid phase extractive preconcentration and separation of uranium(VI).

Amberlite XAD-4 resin has been functionalized with succinic acid by coupling it with dibromosuccinic acid after acetylation. The resulting resin has been characterized by FT-IR, elemental analysis and TGA and has been used for preconcentrative separation of uranium(VI) from host of other inorganic species prior to its determination by spectrophotometry. The optimum pH value for quantitative sorption of uranium(VI) in both batch and column modes is 4.5-8.0 and desorption can be achieved by using 5.0ml of 1.0moll(-1) HCl. The sorption capacity of functionalized resin is 12.3mgg(-1). Calibration graphs were rectilinear over the uranium(VI) concentrations in the range 5-200mugl(-1). Five replicate determinations of 50mug of uranium(VI) present in 1000ml of solution gave a mean absorbance of 0.10 with a relative standard deviation of 2.56%. The detection limit corresponding to three times the standard deviation of the blank was found to be 2mugl(-1). Various cationic and anionic species at 200-fold amounts do not interfere during the preconcentration of 5.0mug of uranium(VI) present in 1000ml (batch) or 100ml (column) of sample solution. Further, adsorption kinetic and isotherm studies were also carried out by a batch method to understand the nature of sorption of uranium(VI) with the succinic acid functionalized resin. The accuracy of the developed solid phase extractive preconcentration method in conjunction with Arsenazo III procedure was tested by analyzing marine sediment (MESS-3) and soil (IAEA soil-7) reference material. Further, the above procedure has been successfully employed for the analysis of soil and sediment samples.

Solid phase extraction preconcentration of cobalt and nickel with 5,7-dichloroquinone-8-ol embedded styrene-ethylene glycol dimethacrylate polymer particles and determination by flame atomic absorption spectrometry (FAAS).

This article explores the synthesis of styrene-divinyl benzene (DVB)/ethylene glycol dimethacrylate (EGDMA) polymers embedded with quinoline-8-ol (Q) or its dihalo derivatives by thermal means in the presence and absence of 4-vinyl pyridine (VP). The above-synthesized polymers were found to enrich cobalt and nickel present in admixtures. Of these, 5,7-dichloroquinoline-8-ol (DCQ) embedded styrene-EGDMA polymer particles enrich cobalt and nickel quantitatively from dilute aqueous solutions within 5 min of preconcentration time. Styrene-EGDMA, DCQ embedded styrene-EGDMA particles obtained by bulk polymerization and cobalt/nickel bonded polymers were characterized by FTIR, thermogravimetric analysis (TGA), elemental analysis and surface area studies. The use of these polymer particles obtained by bulk polymerization for the solid phase extractive preconcentration of cobalt and nickel was investigated in detail and explores the possibility of employing this procedure for the analysis of cobalt and nickel in soil and sediment samples using a simple, low cost and readily available flame atomic absorption spectrometric instrument was explored.

Preconcentrative separation of chromium(VI) species from chromium(III) by coprecipitation of its ethyl xanthate complex onto naphthalene.

A rapid, sensitive and selective method is described for the determination of chromium(VI) in presence of 100-fold amounts of chromium(III) by flame atomic absorption spectrometry (FAAS) in conjunction with coprecipitative preconcentration of its ethyl xanthate complex onto naphthalene. The solid mixture consisting of the chromium(VI) complex together with naphthalene is dissolved in 8.0ml of dimethyl formamide (DMF) and chromium(VI) content was established by FAAS. Calibration graphs were rectilinear over the chromium(VI) concentration in the range 0-200mugl(-1). Five replicate determinations of 20mug of chromium(VI) present in 1.0l of sample solution gave a relative standard deviation of 3.1%. The detection limit corresponding to three times the standard deviation of the blank was found to be 0.5mugl(-1). The developed procedure has been successfully utilized for the estimation of chromium(VI), chromium(total) (after oxidation with bromate) and chromium(III) (by subtracting chromium(VI) content from chromium(total) value contents of several tannery industries.

On-line and off-line preconcentration of trace and ultratrace amounts of lanthanides.

The need for preconcentration of trace and ultratrace amounts of lanthanides from environmental, geological and biological samples is brought out in introductory part. Both on-line and off-line preconcentration procedures developed for lanthanides since 1980 are reviewed. The preconcentration techniques covered in this review include liquid-liquid extraction (LLE), ion-exchange, co-precipitation, and solid phase or solid-liquid extraction. Separate sections are devoted to each of the preconcentration techniques employed for enrichment of individual or mixtures of lanthanides. Future trends in singular or multielement preconcentration of lanthanides are also discussed.

Quinoline-8-ol-immobilized Amberlite XAD-4: synthesis, characterization, and uranyl ion uptake properties suitable for analytical applications.

Amberlite XAD-4 has been functionalized by coupling it with 5-aminoquinoline-8-ol after acetylation. The resulting resin has been characterized by elemental analysis and IR spectra and has been used for preconcentrating uranyl ions prior to its determination by spectrophotometry. The optimum pH value for quantitative sorption is 4-6, and desorption can be achieved by using 5 mL of 1 mol L(-1) HCl. The sorption capacity of the resin is 11.5 mmol g(-1). The effect of various cations and anions on the preconcentration of uranium in conjunction with the determination procedure has been studied and we have found that none of the ions interfere except thorium. The enrichment factor for preconcentration of uranium was found to be 200. Ten replicate determinations of 40 micro g of uranium present in 1 L of sample gave a mean absorbance of 0.185 with a relative standard deviation of 2.64%. The detection limit corresponding to three times the standard deviation of the bank was found to be 2 micro g L(-1). The validation of the developed preconcentration procedure was carried out by successfully analyzing standard marine sediment reference material. The uranyl content of sediment and soils is estimated by spectrophotometry after its preconcentration with the above chelating resin.

Methodologies for the analysis of rare earth elements and their relevance to reference materials.

India has the third largest resources of rare earth elements (REE) in the world. These resources are essentially the monazite sand present in the beaches of southwest, south-east, and mid-eastern coasts of India. Therefore, analytical methodologies for the determination of REE in sea water and high-purity materials were developed. An overview of this work and its relevance to the preparation of standard reference materials of REE in sea water, marine sediments, and high-purity materials in the future is given.

Determination of arsenic in sea water by sorbent extraction with hydride generation atomic absorption spectrometry.

A rapid and sensitive sorbent extraction hydride generation-flow injection analysis atomic absorption spectrometric (HG-FIAS-AAS) method is described for the determination of As(III) and As(V) based upon online preconcentration on a microcolumn packed with activated alumina. In the present procedure these arsenicals are complexed with quinolin-8-ol-5-sulphonic acid from neutral solutions in the flow injection system and adsorbed on the column. The preconcentrated species are eluted with 10% HCl, mixed with 0.5% sodium borohydride and carried to the HG-FIAS cell with a carrier gas flow rate of 75 ml min(-1). The retention efficiency is found to be better than 98% with sensitivity enhancement of 12 and 10 for As(III) and As(V), respectively, for a 20 s preconcentration period. The respective detection limits are 0.05 and 2 ng ml(-1) for As(III) and As(V). The throughput of the samples is found to be 60 h(-1), with a loading time of 20 s. The method has been applied to sea water samples.

Studies on the liquid-liquid extraction of iron(III) and titanium(IV) with 3-phenyl-4-benzoyl-5-isoxazolone.

The extraction behaviour of iron(III) and titanium(IV) from acidic chloride solutions has been investigated using 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) in xylene as an extractant. The results demonstrate that these metal ions are extracted into xylene as Fe(PBI)(3) and TiO(PBI)(2). The equilibrium constants of the extracted complexes have been deduced by non-linear regression analysis by taking into account complexation of metal ion with inorganic ligands in the aqueous phase and all plausible complexes extracted into the organic phase. IR and proton NMR ((1)H NMR) spectra were used to further clarify the nature of complexes extracted into organic phase. The effect of the nature of the diluent on the extraction of iron(III) and titanium(IV) has been studied and correlated with dielectric constants. The extraction behaviour of titanium(IV) has also been compared with that of other metal ions, viz. magnesium(II), vanadium(V), chromium(VI), iron(III), manganese(II), zinc(II) and zirconium(IV), which are associated with the titanium in waste chloride liquors of the titanium-mineral-processing industry.

Application of ternary and multicomponent complexes to spectrophotometric and spectrofluorimetric analysis of inorganics.

The application of ternary and multicomponent complexes in spectrophotometric and spectrofluorimetric determination of trace elements is reviewed. Newer types of colour systems employing mixed ligand, surfactant sensitized, ion-association, flotation, derivative and FIA systems are described. Separate sections are devoted to advances in both spectrophotometric and spectrofluorimetric determination of individual elements. Future trends in spectrophotometric and spectrofluorimetric analysis are discussed.

Ultratrace determination of europium in high-purity lanthanum, praseodymium and dysprosium oxides by luminescence spectrometry.

A luminescence spectrometric method was developed for the determination of ultra trace amounts of europium (down to 1 x 10(-13) M) in high purity lanthanum, praseodymium and dysprosium oxides. This is based on the enhanced luminescence of europium-thenoyltrifluoroacetone (TTA)-dibenzo-18-crown-6 (DBC)-Triton X-100 in the presence of terbium. The fluorescence intensity is linear with europium concentration in the range 1 x 10(-11) - 1 x 10(-6) M under the recommended conditions. The optimized procedure is successfully utilized for the determination of ultratrace amounts of europium in lanthanium, praseodymium and dysprosium oxides.